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ckpts/universal/global_step40/zero/11.input_layernorm.weight/exp_avg.pt

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ckpts/universal/global_step40/zero/11.input_layernorm.weight/exp_avg_sq.pt

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+size 9387

ckpts/universal/global_step40/zero/5.mlp.dense_h_to_4h.weight/fp32.pt

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+size 33555533

venv/lib/python3.10/site-packages/scipy/cluster/tests/test_disjoint_set.py

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+import pytest
+from pytest import raises as assert_raises
+import numpy as np
+from scipy.cluster.hierarchy import DisjointSet
+import string
+
+
+def generate_random_token():
+    k = len(string.ascii_letters)
+    tokens = list(np.arange(k, dtype=int))
+    tokens += list(np.arange(k, dtype=float))
+    tokens += list(string.ascii_letters)
+    tokens += [None for i in range(k)]
+    tokens = np.array(tokens, dtype=object)
+    rng = np.random.RandomState(seed=0)
+
+    while 1:
+        size = rng.randint(1, 3)
+        element = rng.choice(tokens, size)
+        if size == 1:
+            yield element[0]
+        else:
+            yield tuple(element)
+
+
+def get_elements(n):
+    # dict is deterministic without difficulty of comparing numpy ints
+    elements = {}
+    for element in generate_random_token():
+        if element not in elements:
+            elements[element] = len(elements)
+            if len(elements) >= n:
+                break
+    return list(elements.keys())
+
+
+def test_init():
+    n = 10
+    elements = get_elements(n)
+    dis = DisjointSet(elements)
+    assert dis.n_subsets == n
+    assert list(dis) == elements
+
+
+def test_len():
+    n = 10
+    elements = get_elements(n)
+    dis = DisjointSet(elements)
+    assert len(dis) == n
+
+    dis.add("dummy")
+    assert len(dis) == n + 1
+
+
+@pytest.mark.parametrize("n", [10, 100])
+def test_contains(n):
+    elements = get_elements(n)
+    dis = DisjointSet(elements)
+    for x in elements:
+        assert x in dis
+
+    assert "dummy" not in dis
+
+
+@pytest.mark.parametrize("n", [10, 100])
+def test_add(n):
+    elements = get_elements(n)
+    dis1 = DisjointSet(elements)
+
+    dis2 = DisjointSet()
+    for i, x in enumerate(elements):
+        dis2.add(x)
+        assert len(dis2) == i + 1
+
+        # test idempotency by adding element again
+        dis2.add(x)
+        assert len(dis2) == i + 1
+
+    assert list(dis1) == list(dis2)
+
+
+def test_element_not_present():
+    elements = get_elements(n=10)
+    dis = DisjointSet(elements)
+
+    with assert_raises(KeyError):
+        dis["dummy"]
+
+    with assert_raises(KeyError):
+        dis.merge(elements[0], "dummy")
+
+    with assert_raises(KeyError):
+        dis.connected(elements[0], "dummy")
+
+
+@pytest.mark.parametrize("direction", ["forwards", "backwards"])
+@pytest.mark.parametrize("n", [10, 100])
+def test_linear_union_sequence(n, direction):
+    elements = get_elements(n)
+    dis = DisjointSet(elements)
+    assert elements == list(dis)
+
+    indices = list(range(n - 1))
+    if direction == "backwards":
+        indices = indices[::-1]
+
+    for it, i in enumerate(indices):
+        assert not dis.connected(elements[i], elements[i + 1])
+        assert dis.merge(elements[i], elements[i + 1])
+        assert dis.connected(elements[i], elements[i + 1])
+        assert dis.n_subsets == n - 1 - it
+
+    roots = [dis[i] for i in elements]
+    if direction == "forwards":
+        assert all(elements[0] == r for r in roots)
+    else:
+        assert all(elements[-2] == r for r in roots)
+    assert not dis.merge(elements[0], elements[-1])
+
+
+@pytest.mark.parametrize("n", [10, 100])
+def test_self_unions(n):
+    elements = get_elements(n)
+    dis = DisjointSet(elements)
+
+    for x in elements:
+        assert dis.connected(x, x)
+        assert not dis.merge(x, x)
+        assert dis.connected(x, x)
+    assert dis.n_subsets == len(elements)
+
+    assert elements == list(dis)
+    roots = [dis[x] for x in elements]
+    assert elements == roots
+
+
+@pytest.mark.parametrize("order", ["ab", "ba"])
+@pytest.mark.parametrize("n", [10, 100])
+def test_equal_size_ordering(n, order):
+    elements = get_elements(n)
+    dis = DisjointSet(elements)
+
+    rng = np.random.RandomState(seed=0)
+    indices = np.arange(n)
+    rng.shuffle(indices)
+
+    for i in range(0, len(indices), 2):
+        a, b = elements[indices[i]], elements[indices[i + 1]]
+        if order == "ab":
+            assert dis.merge(a, b)
+        else:
+            assert dis.merge(b, a)
+
+        expected = elements[min(indices[i], indices[i + 1])]
+        assert dis[a] == expected
+        assert dis[b] == expected
+
+
+@pytest.mark.parametrize("kmax", [5, 10])
+def test_binary_tree(kmax):
+    n = 2**kmax
+    elements = get_elements(n)
+    dis = DisjointSet(elements)
+    rng = np.random.RandomState(seed=0)
+
+    for k in 2**np.arange(kmax):
+        for i in range(0, n, 2 * k):
+            r1, r2 = rng.randint(0, k, size=2)
+            a, b = elements[i + r1], elements[i + k + r2]
+            assert not dis.connected(a, b)
+            assert dis.merge(a, b)
+            assert dis.connected(a, b)
+
+        assert elements == list(dis)
+        roots = [dis[i] for i in elements]
+        expected_indices = np.arange(n) - np.arange(n) % (2 * k)
+        expected = [elements[i] for i in expected_indices]
+        assert roots == expected
+
+
+@pytest.mark.parametrize("n", [10, 100])
+def test_subsets(n):
+    elements = get_elements(n)
+    dis = DisjointSet(elements)
+
+    rng = np.random.RandomState(seed=0)
+    for i, j in rng.randint(0, n, (n, 2)):
+        x = elements[i]
+        y = elements[j]
+
+        expected = {element for element in dis if {dis[element]} == {dis[x]}}
+        assert dis.subset_size(x) == len(dis.subset(x))
+        assert expected == dis.subset(x)
+
+        expected = {dis[element]: set() for element in dis}
+        for element in dis:
+            expected[dis[element]].add(element)
+        expected = list(expected.values())
+        assert expected == dis.subsets()
+
+        dis.merge(x, y)
+        assert dis.subset(x) == dis.subset(y)

venv/lib/python3.10/site-packages/scipy/cluster/tests/test_vq.py

@@ -0,0 +1,421 @@
+import warnings
+import sys
+from copy import deepcopy
+
+import numpy as np
+from numpy.testing import (
+    assert_array_equal, assert_equal, assert_, suppress_warnings
+)
+import pytest
+from pytest import raises as assert_raises
+
+from scipy.cluster.vq import (kmeans, kmeans2, py_vq, vq, whiten,
+                              ClusterError, _krandinit)
+from scipy.cluster import _vq
+from scipy.conftest import array_api_compatible
+from scipy.sparse._sputils import matrix
+
+from scipy._lib._array_api import (
+    SCIPY_ARRAY_API, copy, cov, xp_assert_close, xp_assert_equal
+)
+
+pytestmark = [array_api_compatible, pytest.mark.usefixtures("skip_if_array_api")]
+skip_if_array_api = pytest.mark.skip_if_array_api
+
+TESTDATA_2D = np.array([
+    -2.2, 1.17, -1.63, 1.69, -2.04, 4.38, -3.09, 0.95, -1.7, 4.79, -1.68, 0.68,
+    -2.26, 3.34, -2.29, 2.55, -1.72, -0.72, -1.99, 2.34, -2.75, 3.43, -2.45,
+    2.41, -4.26, 3.65, -1.57, 1.87, -1.96, 4.03, -3.01, 3.86, -2.53, 1.28,
+    -4.0, 3.95, -1.62, 1.25, -3.42, 3.17, -1.17, 0.12, -3.03, -0.27, -2.07,
+    -0.55, -1.17, 1.34, -2.82, 3.08, -2.44, 0.24, -1.71, 2.48, -5.23, 4.29,
+    -2.08, 3.69, -1.89, 3.62, -2.09, 0.26, -0.92, 1.07, -2.25, 0.88, -2.25,
+    2.02, -4.31, 3.86, -2.03, 3.42, -2.76, 0.3, -2.48, -0.29, -3.42, 3.21,
+    -2.3, 1.73, -2.84, 0.69, -1.81, 2.48, -5.24, 4.52, -2.8, 1.31, -1.67,
+    -2.34, -1.18, 2.17, -2.17, 2.82, -1.85, 2.25, -2.45, 1.86, -6.79, 3.94,
+    -2.33, 1.89, -1.55, 2.08, -1.36, 0.93, -2.51, 2.74, -2.39, 3.92, -3.33,
+    2.99, -2.06, -0.9, -2.83, 3.35, -2.59, 3.05, -2.36, 1.85, -1.69, 1.8,
+    -1.39, 0.66, -2.06, 0.38, -1.47, 0.44, -4.68, 3.77, -5.58, 3.44, -2.29,
+    2.24, -1.04, -0.38, -1.85, 4.23, -2.88, 0.73, -2.59, 1.39, -1.34, 1.75,
+    -1.95, 1.3, -2.45, 3.09, -1.99, 3.41, -5.55, 5.21, -1.73, 2.52, -2.17,
+    0.85, -2.06, 0.49, -2.54, 2.07, -2.03, 1.3, -3.23, 3.09, -1.55, 1.44,
+    -0.81, 1.1, -2.99, 2.92, -1.59, 2.18, -2.45, -0.73, -3.12, -1.3, -2.83,
+    0.2, -2.77, 3.24, -1.98, 1.6, -4.59, 3.39, -4.85, 3.75, -2.25, 1.71, -3.28,
+    3.38, -1.74, 0.88, -2.41, 1.92, -2.24, 1.19, -2.48, 1.06, -1.68, -0.62,
+    -1.3, 0.39, -1.78, 2.35, -3.54, 2.44, -1.32, 0.66, -2.38, 2.76, -2.35,
+    3.95, -1.86, 4.32, -2.01, -1.23, -1.79, 2.76, -2.13, -0.13, -5.25, 3.84,
+    -2.24, 1.59, -4.85, 2.96, -2.41, 0.01, -0.43, 0.13, -3.92, 2.91, -1.75,
+    -0.53, -1.69, 1.69, -1.09, 0.15, -2.11, 2.17, -1.53, 1.22, -2.1, -0.86,
+    -2.56, 2.28, -3.02, 3.33, -1.12, 3.86, -2.18, -1.19, -3.03, 0.79, -0.83,
+    0.97, -3.19, 1.45, -1.34, 1.28, -2.52, 4.22, -4.53, 3.22, -1.97, 1.75,
+    -2.36, 3.19, -0.83, 1.53, -1.59, 1.86, -2.17, 2.3, -1.63, 2.71, -2.03,
+    3.75, -2.57, -0.6, -1.47, 1.33, -1.95, 0.7, -1.65, 1.27, -1.42, 1.09, -3.0,
+    3.87, -2.51, 3.06, -2.6, 0.74, -1.08, -0.03, -2.44, 1.31, -2.65, 2.99,
+    -1.84, 1.65, -4.76, 3.75, -2.07, 3.98, -2.4, 2.67, -2.21, 1.49, -1.21,
+    1.22, -5.29, 2.38, -2.85, 2.28, -5.6, 3.78, -2.7, 0.8, -1.81, 3.5, -3.75,
+    4.17, -1.29, 2.99, -5.92, 3.43, -1.83, 1.23, -1.24, -1.04, -2.56, 2.37,
+    -3.26, 0.39, -4.63, 2.51, -4.52, 3.04, -1.7, 0.36, -1.41, 0.04, -2.1, 1.0,
+    -1.87, 3.78, -4.32, 3.59, -2.24, 1.38, -1.99, -0.22, -1.87, 1.95, -0.84,
+    2.17, -5.38, 3.56, -1.27, 2.9, -1.79, 3.31, -5.47, 3.85, -1.44, 3.69,
+    -2.02, 0.37, -1.29, 0.33, -2.34, 2.56, -1.74, -1.27, -1.97, 1.22, -2.51,
+    -0.16, -1.64, -0.96, -2.99, 1.4, -1.53, 3.31, -2.24, 0.45, -2.46, 1.71,
+    -2.88, 1.56, -1.63, 1.46, -1.41, 0.68, -1.96, 2.76, -1.61,
+    2.11]).reshape((200, 2))
+
+
+# Global data
+X = np.array([[3.0, 3], [4, 3], [4, 2],
+              [9, 2], [5, 1], [6, 2], [9, 4],
+              [5, 2], [5, 4], [7, 4], [6, 5]])
+
+CODET1 = np.array([[3.0000, 3.0000],
+                   [6.2000, 4.0000],
+                   [5.8000, 1.8000]])
+
+CODET2 = np.array([[11.0/3, 8.0/3],
+                   [6.7500, 4.2500],
+                   [6.2500, 1.7500]])
+
+LABEL1 = np.array([0, 1, 2, 2, 2, 2, 1, 2, 1, 1, 1])
+
+
+class TestWhiten:
+
+    def test_whiten(self, xp):
+        desired = xp.asarray([[5.08738849, 2.97091878],
+                            [3.19909255, 0.69660580],
+                            [4.51041982, 0.02640918],
+                            [4.38567074, 0.95120889],
+                            [2.32191480, 1.63195503]])
+
+        obs = xp.asarray([[0.98744510, 0.82766775],
+                          [0.62093317, 0.19406729],
+                          [0.87545741, 0.00735733],
+                          [0.85124403, 0.26499712],
+                          [0.45067590, 0.45464607]])
+        xp_assert_close(whiten(obs), desired, rtol=1e-5)
+
+    def test_whiten_zero_std(self, xp):
+        desired = xp.asarray([[0., 1.0, 2.86666544],
+                              [0., 1.0, 1.32460034],
+                              [0., 1.0, 3.74382172]])
+
+        obs = xp.asarray([[0., 1., 0.74109533],
+                          [0., 1., 0.34243798],
+                          [0., 1., 0.96785929]])
+        with warnings.catch_warnings(record=True) as w:
+            warnings.simplefilter('always')
+
+            xp_assert_close(whiten(obs), desired, rtol=1e-5)
+
+            assert_equal(len(w), 1)
+            assert_(issubclass(w[-1].category, RuntimeWarning))
+
+    def test_whiten_not_finite(self, xp):
+        for bad_value in xp.nan, xp.inf, -xp.inf:
+            obs = xp.asarray([[0.98744510, bad_value],
+                              [0.62093317, 0.19406729],
+                              [0.87545741, 0.00735733],
+                              [0.85124403, 0.26499712],
+                              [0.45067590, 0.45464607]])
+            assert_raises(ValueError, whiten, obs)
+
+    @pytest.mark.skipif(SCIPY_ARRAY_API,
+                        reason='`np.matrix` unsupported in array API mode')
+    def test_whiten_not_finite_matrix(self, xp):
+        for bad_value in np.nan, np.inf, -np.inf:
+            obs = matrix([[0.98744510, bad_value],
+                          [0.62093317, 0.19406729],
+                          [0.87545741, 0.00735733],
+                          [0.85124403, 0.26499712],
+                          [0.45067590, 0.45464607]])
+            assert_raises(ValueError, whiten, obs)
+
+
+class TestVq:
+
+    @skip_if_array_api(cpu_only=True)
+    def test_py_vq(self, xp):
+        initc = np.concatenate([[X[0]], [X[1]], [X[2]]])
+        # label1.dtype varies between int32 and int64 over platforms
+        label1 = py_vq(xp.asarray(X), xp.asarray(initc))[0]
+        xp_assert_equal(label1, xp.asarray(LABEL1, dtype=xp.int64),
+                        check_dtype=False)
+
+    @pytest.mark.skipif(SCIPY_ARRAY_API,
+                        reason='`np.matrix` unsupported in array API mode')
+    def test_py_vq_matrix(self, xp):
+        initc = np.concatenate([[X[0]], [X[1]], [X[2]]])
+        # label1.dtype varies between int32 and int64 over platforms
+        label1 = py_vq(matrix(X), matrix(initc))[0]
+        assert_array_equal(label1, LABEL1)
+
+    @skip_if_array_api(np_only=True, reasons=['`_vq` only supports NumPy backend'])
+    def test_vq(self, xp):
+        initc = np.concatenate([[X[0]], [X[1]], [X[2]]])
+        label1, _ = _vq.vq(xp.asarray(X), xp.asarray(initc))
+        assert_array_equal(label1, LABEL1)
+        _, _ = vq(xp.asarray(X), xp.asarray(initc))
+
+    @pytest.mark.skipif(SCIPY_ARRAY_API,
+                        reason='`np.matrix` unsupported in array API mode')
+    def test_vq_matrix(self, xp):
+        initc = np.concatenate([[X[0]], [X[1]], [X[2]]])
+        label1, _ = _vq.vq(matrix(X), matrix(initc))
+        assert_array_equal(label1, LABEL1)
+        _, _ = vq(matrix(X), matrix(initc))
+
+    @skip_if_array_api(cpu_only=True)
+    def test_vq_1d(self, xp):
+        # Test special rank 1 vq algo, python implementation.
+        data = X[:, 0]
+        initc = data[:3]
+        a, b = _vq.vq(data, initc)
+        data = xp.asarray(data)
+        initc = xp.asarray(initc)
+        ta, tb = py_vq(data[:, np.newaxis], initc[:, np.newaxis])
+        # ta.dtype varies between int32 and int64 over platforms
+        xp_assert_equal(ta, xp.asarray(a, dtype=xp.int64), check_dtype=False)
+        xp_assert_equal(tb, xp.asarray(b))
+
+    @skip_if_array_api(np_only=True, reasons=['`_vq` only supports NumPy backend'])
+    def test__vq_sametype(self, xp):
+        a = xp.asarray([1.0, 2.0], dtype=xp.float64)
+        b = a.astype(xp.float32)
+        assert_raises(TypeError, _vq.vq, a, b)
+
+    @skip_if_array_api(np_only=True, reasons=['`_vq` only supports NumPy backend'])
+    def test__vq_invalid_type(self, xp):
+        a = xp.asarray([1, 2], dtype=int)
+        assert_raises(TypeError, _vq.vq, a, a)
+
+    @skip_if_array_api(cpu_only=True)
+    def test_vq_large_nfeat(self, xp):
+        X = np.random.rand(20, 20)
+        code_book = np.random.rand(3, 20)
+
+        codes0, dis0 = _vq.vq(X, code_book)
+        codes1, dis1 = py_vq(
+            xp.asarray(X), xp.asarray(code_book)
+        )
+        xp_assert_close(dis1, xp.asarray(dis0), rtol=1e-5)
+        # codes1.dtype varies between int32 and int64 over platforms
+        xp_assert_equal(codes1, xp.asarray(codes0, dtype=xp.int64), check_dtype=False)
+
+        X = X.astype(np.float32)
+        code_book = code_book.astype(np.float32)
+
+        codes0, dis0 = _vq.vq(X, code_book)
+        codes1, dis1 = py_vq(
+            xp.asarray(X), xp.asarray(code_book)
+        )
+        xp_assert_close(dis1, xp.asarray(dis0, dtype=xp.float64), rtol=1e-5)
+        # codes1.dtype varies between int32 and int64 over platforms
+        xp_assert_equal(codes1, xp.asarray(codes0, dtype=xp.int64), check_dtype=False)
+
+    @skip_if_array_api(cpu_only=True)
+    def test_vq_large_features(self, xp):
+        X = np.random.rand(10, 5) * 1000000
+        code_book = np.random.rand(2, 5) * 1000000
+
+        codes0, dis0 = _vq.vq(X, code_book)
+        codes1, dis1 = py_vq(
+            xp.asarray(X), xp.asarray(code_book)
+        )
+        xp_assert_close(dis1, xp.asarray(dis0), rtol=1e-5)
+        # codes1.dtype varies between int32 and int64 over platforms
+        xp_assert_equal(codes1, xp.asarray(codes0, dtype=xp.int64), check_dtype=False)
+
+
+# Whole class skipped on GPU for now;
+# once pdist/cdist are hooked up for CuPy, more tests will work
+@skip_if_array_api(cpu_only=True)
+class TestKMean:
+
+    def test_large_features(self, xp):
+        # Generate a data set with large values, and run kmeans on it to
+        # (regression for 1077).
+        d = 300
+        n = 100
+
+        m1 = np.random.randn(d)
+        m2 = np.random.randn(d)
+        x = 10000 * np.random.randn(n, d) - 20000 * m1
+        y = 10000 * np.random.randn(n, d) + 20000 * m2
+
+        data = np.empty((x.shape[0] + y.shape[0], d), np.float64)
+        data[:x.shape[0]] = x
+        data[x.shape[0]:] = y
+
+        kmeans(xp.asarray(data), 2)
+
+    def test_kmeans_simple(self, xp):
+        np.random.seed(54321)
+        initc = np.concatenate([[X[0]], [X[1]], [X[2]]])
+        code1 = kmeans(xp.asarray(X), xp.asarray(initc), iter=1)[0]
+        xp_assert_close(code1, xp.asarray(CODET2))
+
+    @pytest.mark.skipif(SCIPY_ARRAY_API,
+                        reason='`np.matrix` unsupported in array API mode')
+    def test_kmeans_simple_matrix(self, xp):
+        np.random.seed(54321)
+        initc = np.concatenate([[X[0]], [X[1]], [X[2]]])
+        code1 = kmeans(matrix(X), matrix(initc), iter=1)[0]
+        xp_assert_close(code1, CODET2)
+
+    def test_kmeans_lost_cluster(self, xp):
+        # This will cause kmeans to have a cluster with no points.
+        data = xp.asarray(TESTDATA_2D)
+        initk = xp.asarray([[-1.8127404, -0.67128041],
+                            [2.04621601, 0.07401111],
+                            [-2.31149087, -0.05160469]])
+
+        kmeans(data, initk)
+        with suppress_warnings() as sup:
+            sup.filter(UserWarning,
+                       "One of the clusters is empty. Re-run kmeans with a "
+                       "different initialization")
+            kmeans2(data, initk, missing='warn')
+
+        assert_raises(ClusterError, kmeans2, data, initk, missing='raise')
+
+    def test_kmeans2_simple(self, xp):
+        np.random.seed(12345678)
+        initc = xp.asarray(np.concatenate([[X[0]], [X[1]], [X[2]]]))
+        arrays = [xp.asarray] if SCIPY_ARRAY_API else [np.asarray, matrix]
+        for tp in arrays:
+            code1 = kmeans2(tp(X), tp(initc), iter=1)[0]
+            code2 = kmeans2(tp(X), tp(initc), iter=2)[0]
+
+            xp_assert_close(code1, xp.asarray(CODET1))
+            xp_assert_close(code2, xp.asarray(CODET2))
+
+    @pytest.mark.skipif(SCIPY_ARRAY_API,
+                        reason='`np.matrix` unsupported in array API mode')
+    def test_kmeans2_simple_matrix(self, xp):
+        np.random.seed(12345678)
+        initc = xp.asarray(np.concatenate([[X[0]], [X[1]], [X[2]]]))
+        code1 = kmeans2(matrix(X), matrix(initc), iter=1)[0]
+        code2 = kmeans2(matrix(X), matrix(initc), iter=2)[0]
+
+        xp_assert_close(code1, CODET1)
+        xp_assert_close(code2, CODET2)
+
+    def test_kmeans2_rank1(self, xp):
+        data = xp.asarray(TESTDATA_2D)
+        data1 = data[:, 0]
+
+        initc = data1[:3]
+        code = copy(initc, xp=xp)
+        kmeans2(data1, code, iter=1)[0]
+        kmeans2(data1, code, iter=2)[0]
+
+    def test_kmeans2_rank1_2(self, xp):
+        data = xp.asarray(TESTDATA_2D)
+        data1 = data[:, 0]
+        kmeans2(data1, 2, iter=1)
+
+    def test_kmeans2_high_dim(self, xp):
+        # test kmeans2 when the number of dimensions exceeds the number
+        # of input points
+        data = xp.asarray(TESTDATA_2D)
+        data = xp.reshape(data, (20, 20))[:10, :]
+        kmeans2(data, 2)
+
+    def test_kmeans2_init(self, xp):
+        np.random.seed(12345)
+        data = xp.asarray(TESTDATA_2D)
+        k = 3
+
+        kmeans2(data, k, minit='points')
+        kmeans2(data[:, 1], k, minit='points')  # special case (1-D)
+
+        kmeans2(data, k, minit='++')
+        kmeans2(data[:, 1], k, minit='++')  # special case (1-D)
+
+        # minit='random' can give warnings, filter those
+        with suppress_warnings() as sup:
+            sup.filter(message="One of the clusters is empty. Re-run.")
+            kmeans2(data, k, minit='random')
+            kmeans2(data[:, 1], k, minit='random')  # special case (1-D)
+
+    @pytest.mark.skipif(sys.platform == 'win32',
+                        reason='Fails with MemoryError in Wine.')
+    def test_krandinit(self, xp):
+        data = xp.asarray(TESTDATA_2D)
+        datas = [xp.reshape(data, (200, 2)),
+                 xp.reshape(data, (20, 20))[:10, :]]
+        k = int(1e6)
+        for data in datas:
+            rng = np.random.default_rng(1234)
+            init = _krandinit(data, k, rng, xp)
+            orig_cov = cov(data.T)
+            init_cov = cov(init.T)
+            xp_assert_close(orig_cov, init_cov, atol=1e-2)
+
+    def test_kmeans2_empty(self, xp):
+        # Regression test for gh-1032.
+        assert_raises(ValueError, kmeans2, xp.asarray([]), 2)
+
+    def test_kmeans_0k(self, xp):
+        # Regression test for gh-1073: fail when k arg is 0.
+        assert_raises(ValueError, kmeans, xp.asarray(X), 0)
+        assert_raises(ValueError, kmeans2, xp.asarray(X), 0)
+        assert_raises(ValueError, kmeans2, xp.asarray(X), xp.asarray([]))
+
+    def test_kmeans_large_thres(self, xp):
+        # Regression test for gh-1774
+        x = xp.asarray([1, 2, 3, 4, 10], dtype=xp.float64)
+        res = kmeans(x, 1, thresh=1e16)
+        xp_assert_close(res[0], xp.asarray([4.], dtype=xp.float64))
+        xp_assert_close(res[1], xp.asarray(2.3999999999999999, dtype=xp.float64)[()])
+
+    def test_kmeans2_kpp_low_dim(self, xp):
+        # Regression test for gh-11462
+        prev_res = xp.asarray([[-1.95266667, 0.898],
+                               [-3.153375, 3.3945]], dtype=xp.float64)
+        np.random.seed(42)
+        res, _ = kmeans2(xp.asarray(TESTDATA_2D), 2, minit='++')
+        xp_assert_close(res, prev_res)
+
+    def test_kmeans2_kpp_high_dim(self, xp):
+        # Regression test for gh-11462
+        n_dim = 100
+        size = 10
+        centers = np.vstack([5 * np.ones(n_dim),
+                             -5 * np.ones(n_dim)])
+        np.random.seed(42)
+        data = np.vstack([
+            np.random.multivariate_normal(centers[0], np.eye(n_dim), size=size),
+            np.random.multivariate_normal(centers[1], np.eye(n_dim), size=size)
+        ])
+
+        data = xp.asarray(data)
+        res, _ = kmeans2(data, 2, minit='++')
+        xp_assert_equal(xp.sign(res), xp.sign(xp.asarray(centers)))
+
+    def test_kmeans_diff_convergence(self, xp):
+        # Regression test for gh-8727
+        obs = xp.asarray([-3, -1, 0, 1, 1, 8], dtype=xp.float64)
+        res = kmeans(obs, xp.asarray([-3., 0.99]))
+        xp_assert_close(res[0], xp.asarray([-0.4,  8.], dtype=xp.float64))
+        xp_assert_close(res[1], xp.asarray(1.0666666666666667, dtype=xp.float64)[()])
+
+    def test_kmeans_and_kmeans2_random_seed(self, xp):
+
+        seed_list = [
+            1234, np.random.RandomState(1234), np.random.default_rng(1234)
+        ]
+
+        for seed in seed_list:
+            seed1 = deepcopy(seed)
+            seed2 = deepcopy(seed)
+            data = xp.asarray(TESTDATA_2D)
+            # test for kmeans
+            res1, _ = kmeans(data, 2, seed=seed1)
+            res2, _ = kmeans(data, 2, seed=seed2)
+            xp_assert_close(res1, res2, xp=xp)  # should be same results
+            # test for kmeans2
+            for minit in ["random", "points", "++"]:
+                res1, _ = kmeans2(data, 2, minit=minit, seed=seed1)
+                res2, _ = kmeans2(data, 2, minit=minit, seed=seed2)
+                xp_assert_close(res1, res2, xp=xp)  # should be same results

venv/lib/python3.10/site-packages/scipy/interpolate/__init__.py

@@ -0,0 +1,201 @@
+"""
+========================================
+Interpolation (:mod:`scipy.interpolate`)
+========================================
+
+.. currentmodule:: scipy.interpolate
+
+Sub-package for objects used in interpolation.
+
+As listed below, this sub-package contains spline functions and classes,
+1-D and multidimensional (univariate and multivariate)
+interpolation classes, Lagrange and Taylor polynomial interpolators, and
+wrappers for `FITPACK <http://www.netlib.org/dierckx/>`__
+and DFITPACK functions.
+
+Univariate interpolation
+========================
+
+.. autosummary::
+   :toctree: generated/
+
+   interp1d
+   BarycentricInterpolator
+   KroghInterpolator
+   barycentric_interpolate
+   krogh_interpolate
+   pchip_interpolate
+   CubicHermiteSpline
+   PchipInterpolator
+   Akima1DInterpolator
+   CubicSpline
+   PPoly
+   BPoly
+
+
+Multivariate interpolation
+==========================
+
+Unstructured data:
+
+.. autosummary::
+   :toctree: generated/
+
+   griddata
+   LinearNDInterpolator
+   NearestNDInterpolator
+   CloughTocher2DInterpolator
+   RBFInterpolator
+   Rbf
+   interp2d
+
+For data on a grid:
+
+.. autosummary::
+   :toctree: generated/
+
+   interpn
+   RegularGridInterpolator
+   RectBivariateSpline
+
+.. seealso::
+
+    `scipy.ndimage.map_coordinates`
+
+Tensor product polynomials:
+
+.. autosummary::
+   :toctree: generated/
+
+   NdPPoly
+   NdBSpline
+
+1-D Splines
+===========
+
+.. autosummary::
+   :toctree: generated/
+
+   BSpline
+   make_interp_spline
+   make_lsq_spline
+   make_smoothing_spline
+
+Functional interface to FITPACK routines:
+
+.. autosummary::
+   :toctree: generated/
+
+   splrep
+   splprep
+   splev
+   splint
+   sproot
+   spalde
+   splder
+   splantider
+   insert
+
+Object-oriented FITPACK interface:
+
+.. autosummary::
+   :toctree: generated/
+
+   UnivariateSpline
+   InterpolatedUnivariateSpline
+   LSQUnivariateSpline
+
+
+
+2-D Splines
+===========
+
+For data on a grid:
+
+.. autosummary::
+   :toctree: generated/
+
+   RectBivariateSpline
+   RectSphereBivariateSpline
+
+For unstructured data:
+
+.. autosummary::
+   :toctree: generated/
+
+   BivariateSpline
+   SmoothBivariateSpline
+   SmoothSphereBivariateSpline
+   LSQBivariateSpline
+   LSQSphereBivariateSpline
+
+Low-level interface to FITPACK functions:
+
+.. autosummary::
+   :toctree: generated/
+
+   bisplrep
+   bisplev
+
+Additional tools
+================
+
+.. autosummary::
+   :toctree: generated/
+
+   lagrange
+   approximate_taylor_polynomial
+   pade
+
+.. seealso::
+
+   `scipy.ndimage.map_coordinates`,
+   `scipy.ndimage.spline_filter`,
+   `scipy.signal.resample`,
+   `scipy.signal.bspline`,
+   `scipy.signal.gauss_spline`,
+   `scipy.signal.qspline1d`,
+   `scipy.signal.cspline1d`,
+   `scipy.signal.qspline1d_eval`,
+   `scipy.signal.cspline1d_eval`,
+   `scipy.signal.qspline2d`,
+   `scipy.signal.cspline2d`.
+
+``pchip`` is an alias of `PchipInterpolator` for backward compatibility
+(should not be used in new code).
+"""
+from ._interpolate import *
+from ._fitpack_py import *
+
+# New interface to fitpack library:
+from ._fitpack2 import *
+
+from ._rbf import Rbf
+
+from ._rbfinterp import *
+
+from ._polyint import *
+
+from ._cubic import *
+
+from ._ndgriddata import *
+
+from ._bsplines import *
+
+from ._pade import *
+
+from ._rgi import *
+
+from ._ndbspline import NdBSpline
+
+# Deprecated namespaces, to be removed in v2.0.0
+from . import fitpack, fitpack2, interpolate, ndgriddata, polyint, rbf
+
+__all__ = [s for s in dir() if not s.startswith('_')]
+
+from scipy._lib._testutils import PytestTester
+test = PytestTester(__name__)
+del PytestTester
+
+# Backward compatibility
+pchip = PchipInterpolator

venv/lib/python3.10/site-packages/scipy/interpolate/_bsplines.py

@@ -0,0 +1,2215 @@
+import operator
+from math import prod
+
+import numpy as np
+from scipy._lib._util import normalize_axis_index
+from scipy.linalg import (get_lapack_funcs, LinAlgError,
+                          cholesky_banded, cho_solve_banded,
+                          solve, solve_banded)
+from scipy.optimize import minimize_scalar
+from . import _bspl
+from . import _fitpack_impl
+from scipy.sparse import csr_array
+from scipy.special import poch
+from itertools import combinations
+
+__all__ = ["BSpline", "make_interp_spline", "make_lsq_spline",
+           "make_smoothing_spline"]
+
+
+def _get_dtype(dtype):
+    """Return np.complex128 for complex dtypes, np.float64 otherwise."""
+    if np.issubdtype(dtype, np.complexfloating):
+        return np.complex128
+    else:
+        return np.float64
+
+
+def _as_float_array(x, check_finite=False):
+    """Convert the input into a C contiguous float array.
+
+    NB: Upcasts half- and single-precision floats to double precision.
+    """
+    x = np.ascontiguousarray(x)
+    dtyp = _get_dtype(x.dtype)
+    x = x.astype(dtyp, copy=False)
+    if check_finite and not np.isfinite(x).all():
+        raise ValueError("Array must not contain infs or nans.")
+    return x
+
+
+def _dual_poly(j, k, t, y):
+    """
+    Dual polynomial of the B-spline B_{j,k,t} -
+    polynomial which is associated with B_{j,k,t}:
+    $p_{j,k}(y) = (y - t_{j+1})(y - t_{j+2})...(y - t_{j+k})$
+    """
+    if k == 0:
+        return 1
+    return np.prod([(y - t[j + i]) for i in range(1, k + 1)])
+
+
+def _diff_dual_poly(j, k, y, d, t):
+    """
+    d-th derivative of the dual polynomial $p_{j,k}(y)$
+    """
+    if d == 0:
+        return _dual_poly(j, k, t, y)
+    if d == k:
+        return poch(1, k)
+    comb = list(combinations(range(j + 1, j + k + 1), d))
+    res = 0
+    for i in range(len(comb) * len(comb[0])):
+        res += np.prod([(y - t[j + p]) for p in range(1, k + 1)
+                        if (j + p) not in comb[i//d]])
+    return res
+
+
+class BSpline:
+    r"""Univariate spline in the B-spline basis.
+
+    .. math::
+
+        S(x) = \sum_{j=0}^{n-1} c_j  B_{j, k; t}(x)
+
+    where :math:`B_{j, k; t}` are B-spline basis functions of degree `k`
+    and knots `t`.
+
+    Parameters
+    ----------
+    t : ndarray, shape (n+k+1,)
+        knots
+    c : ndarray, shape (>=n, ...)
+        spline coefficients
+    k : int
+        B-spline degree
+    extrapolate : bool or 'periodic', optional
+        whether to extrapolate beyond the base interval, ``t[k] .. t[n]``,
+        or to return nans.
+        If True, extrapolates the first and last polynomial pieces of b-spline
+        functions active on the base interval.
+        If 'periodic', periodic extrapolation is used.
+        Default is True.
+    axis : int, optional
+        Interpolation axis. Default is zero.
+
+    Attributes
+    ----------
+    t : ndarray
+        knot vector
+    c : ndarray
+        spline coefficients
+    k : int
+        spline degree
+    extrapolate : bool
+        If True, extrapolates the first and last polynomial pieces of b-spline
+        functions active on the base interval.
+    axis : int
+        Interpolation axis.
+    tck : tuple
+        A read-only equivalent of ``(self.t, self.c, self.k)``
+
+    Methods
+    -------
+    __call__
+    basis_element
+    derivative
+    antiderivative
+    integrate
+    insert_knot
+    construct_fast
+    design_matrix
+    from_power_basis
+
+    Notes
+    -----
+    B-spline basis elements are defined via
+
+    .. math::
+
+        B_{i, 0}(x) = 1, \textrm{if $t_i \le x < t_{i+1}$, otherwise $0$,}
+
+        B_{i, k}(x) = \frac{x - t_i}{t_{i+k} - t_i} B_{i, k-1}(x)
+                 + \frac{t_{i+k+1} - x}{t_{i+k+1} - t_{i+1}} B_{i+1, k-1}(x)
+
+    **Implementation details**
+
+    - At least ``k+1`` coefficients are required for a spline of degree `k`,
+      so that ``n >= k+1``. Additional coefficients, ``c[j]`` with
+      ``j > n``, are ignored.
+
+    - B-spline basis elements of degree `k` form a partition of unity on the
+      *base interval*, ``t[k] <= x <= t[n]``.
+
+
+    Examples
+    --------
+
+    Translating the recursive definition of B-splines into Python code, we have:
+
+    >>> def B(x, k, i, t):
+    ...    if k == 0:
+    ...       return 1.0 if t[i] <= x < t[i+1] else 0.0
+    ...    if t[i+k] == t[i]:
+    ...       c1 = 0.0
+    ...    else:
+    ...       c1 = (x - t[i])/(t[i+k] - t[i]) * B(x, k-1, i, t)
+    ...    if t[i+k+1] == t[i+1]:
+    ...       c2 = 0.0
+    ...    else:
+    ...       c2 = (t[i+k+1] - x)/(t[i+k+1] - t[i+1]) * B(x, k-1, i+1, t)
+    ...    return c1 + c2
+
+    >>> def bspline(x, t, c, k):
+    ...    n = len(t) - k - 1
+    ...    assert (n >= k+1) and (len(c) >= n)
+    ...    return sum(c[i] * B(x, k, i, t) for i in range(n))
+
+    Note that this is an inefficient (if straightforward) way to
+    evaluate B-splines --- this spline class does it in an equivalent,
+    but much more efficient way.
+
+    Here we construct a quadratic spline function on the base interval
+    ``2 <= x <= 4`` and compare with the naive way of evaluating the spline:
+
+    >>> from scipy.interpolate import BSpline
+    >>> k = 2
+    >>> t = [0, 1, 2, 3, 4, 5, 6]
+    >>> c = [-1, 2, 0, -1]
+    >>> spl = BSpline(t, c, k)
+    >>> spl(2.5)
+    array(1.375)
+    >>> bspline(2.5, t, c, k)
+    1.375
+
+    Note that outside of the base interval results differ. This is because
+    `BSpline` extrapolates the first and last polynomial pieces of B-spline
+    functions active on the base interval.
+
+    >>> import matplotlib.pyplot as plt
+    >>> import numpy as np
+    >>> fig, ax = plt.subplots()
+    >>> xx = np.linspace(1.5, 4.5, 50)
+    >>> ax.plot(xx, [bspline(x, t, c ,k) for x in xx], 'r-', lw=3, label='naive')
+    >>> ax.plot(xx, spl(xx), 'b-', lw=4, alpha=0.7, label='BSpline')
+    >>> ax.grid(True)
+    >>> ax.legend(loc='best')
+    >>> plt.show()
+
+
+    References
+    ----------
+    .. [1] Tom Lyche and Knut Morken, Spline methods,
+        http://www.uio.no/studier/emner/matnat/ifi/INF-MAT5340/v05/undervisningsmateriale/
+    .. [2] Carl de Boor, A practical guide to splines, Springer, 2001.
+
+    """
+
+    def __init__(self, t, c, k, extrapolate=True, axis=0):
+        super().__init__()
+
+        self.k = operator.index(k)
+        self.c = np.asarray(c)
+        self.t = np.ascontiguousarray(t, dtype=np.float64)
+
+        if extrapolate == 'periodic':
+            self.extrapolate = extrapolate
+        else:
+            self.extrapolate = bool(extrapolate)
+
+        n = self.t.shape[0] - self.k - 1
+
+        axis = normalize_axis_index(axis, self.c.ndim)
+
+        # Note that the normalized axis is stored in the object.
+        self.axis = axis
+        if axis != 0:
+            # roll the interpolation axis to be the first one in self.c
+            # More specifically, the target shape for self.c is (n, ...),
+            # and axis !=0 means that we have c.shape (..., n, ...)
+            #                                               ^
+            #                                              axis
+            self.c = np.moveaxis(self.c, axis, 0)
+
+        if k < 0:
+            raise ValueError("Spline order cannot be negative.")
+        if self.t.ndim != 1:
+            raise ValueError("Knot vector must be one-dimensional.")
+        if n < self.k + 1:
+            raise ValueError("Need at least %d knots for degree %d" %
+                             (2*k + 2, k))
+        if (np.diff(self.t) < 0).any():
+            raise ValueError("Knots must be in a non-decreasing order.")
+        if len(np.unique(self.t[k:n+1])) < 2:
+            raise ValueError("Need at least two internal knots.")
+        if not np.isfinite(self.t).all():
+            raise ValueError("Knots should not have nans or infs.")
+        if self.c.ndim < 1:
+            raise ValueError("Coefficients must be at least 1-dimensional.")
+        if self.c.shape[0] < n:
+            raise ValueError("Knots, coefficients and degree are inconsistent.")
+
+        dt = _get_dtype(self.c.dtype)
+        self.c = np.ascontiguousarray(self.c, dtype=dt)
+
+    @classmethod
+    def construct_fast(cls, t, c, k, extrapolate=True, axis=0):
+        """Construct a spline without making checks.
+
+        Accepts same parameters as the regular constructor. Input arrays
+        `t` and `c` must of correct shape and dtype.
+        """
+        self = object.__new__(cls)
+        self.t, self.c, self.k = t, c, k
+        self.extrapolate = extrapolate
+        self.axis = axis
+        return self
+
+    @property
+    def tck(self):
+        """Equivalent to ``(self.t, self.c, self.k)`` (read-only).
+        """
+        return self.t, self.c, self.k
+
+    @classmethod
+    def basis_element(cls, t, extrapolate=True):
+        """Return a B-spline basis element ``B(x | t[0], ..., t[k+1])``.
+
+        Parameters
+        ----------
+        t : ndarray, shape (k+2,)
+            internal knots
+        extrapolate : bool or 'periodic', optional
+            whether to extrapolate beyond the base interval, ``t[0] .. t[k+1]``,
+            or to return nans.
+            If 'periodic', periodic extrapolation is used.
+            Default is True.
+
+        Returns
+        -------
+        basis_element : callable
+            A callable representing a B-spline basis element for the knot
+            vector `t`.
+
+        Notes
+        -----
+        The degree of the B-spline, `k`, is inferred from the length of `t` as
+        ``len(t)-2``. The knot vector is constructed by appending and prepending
+        ``k+1`` elements to internal knots `t`.
+
+        Examples
+        --------
+
+        Construct a cubic B-spline:
+
+        >>> import numpy as np
+        >>> from scipy.interpolate import BSpline
+        >>> b = BSpline.basis_element([0, 1, 2, 3, 4])
+        >>> k = b.k
+        >>> b.t[k:-k]
+        array([ 0.,  1.,  2.,  3.,  4.])
+        >>> k
+        3
+
+        Construct a quadratic B-spline on ``[0, 1, 1, 2]``, and compare
+        to its explicit form:
+
+        >>> t = [0, 1, 1, 2]
+        >>> b = BSpline.basis_element(t)
+        >>> def f(x):
+        ...     return np.where(x < 1, x*x, (2. - x)**2)
+
+        >>> import matplotlib.pyplot as plt
+        >>> fig, ax = plt.subplots()
+        >>> x = np.linspace(0, 2, 51)
+        >>> ax.plot(x, b(x), 'g', lw=3)
+        >>> ax.plot(x, f(x), 'r', lw=8, alpha=0.4)
+        >>> ax.grid(True)
+        >>> plt.show()
+
+        """
+        k = len(t) - 2
+        t = _as_float_array(t)
+        t = np.r_[(t[0]-1,) * k, t, (t[-1]+1,) * k]
+        c = np.zeros_like(t)
+        c[k] = 1.
+        return cls.construct_fast(t, c, k, extrapolate)
+
+    @classmethod
+    def design_matrix(cls, x, t, k, extrapolate=False):
+        """
+        Returns a design matrix as a CSR format sparse array.
+
+        Parameters
+        ----------
+        x : array_like, shape (n,)
+            Points to evaluate the spline at.
+        t : array_like, shape (nt,)
+            Sorted 1D array of knots.
+        k : int
+            B-spline degree.
+        extrapolate : bool or 'periodic', optional
+            Whether to extrapolate based on the first and last intervals
+            or raise an error. If 'periodic', periodic extrapolation is used.
+            Default is False.
+
+            .. versionadded:: 1.10.0
+
+        Returns
+        -------
+        design_matrix : `csr_array` object
+            Sparse matrix in CSR format where each row contains all the basis
+            elements of the input row (first row = basis elements of x[0],
+            ..., last row = basis elements x[-1]).
+
+        Examples
+        --------
+        Construct a design matrix for a B-spline
+
+        >>> from scipy.interpolate import make_interp_spline, BSpline
+        >>> import numpy as np
+        >>> x = np.linspace(0, np.pi * 2, 4)
+        >>> y = np.sin(x)
+        >>> k = 3
+        >>> bspl = make_interp_spline(x, y, k=k)
+        >>> design_matrix = bspl.design_matrix(x, bspl.t, k)
+        >>> design_matrix.toarray()
+        [[1.        , 0.        , 0.        , 0.        ],
+        [0.2962963 , 0.44444444, 0.22222222, 0.03703704],
+        [0.03703704, 0.22222222, 0.44444444, 0.2962963 ],
+        [0.        , 0.        , 0.        , 1.        ]]
+
+        Construct a design matrix for some vector of knots
+
+        >>> k = 2
+        >>> t = [-1, 0, 1, 2, 3, 4, 5, 6]
+        >>> x = [1, 2, 3, 4]
+        >>> design_matrix = BSpline.design_matrix(x, t, k).toarray()
+        >>> design_matrix
+        [[0.5, 0.5, 0. , 0. , 0. ],
+        [0. , 0.5, 0.5, 0. , 0. ],
+        [0. , 0. , 0.5, 0.5, 0. ],
+        [0. , 0. , 0. , 0.5, 0.5]]
+
+        This result is equivalent to the one created in the sparse format
+
+        >>> c = np.eye(len(t) - k - 1)
+        >>> design_matrix_gh = BSpline(t, c, k)(x)
+        >>> np.allclose(design_matrix, design_matrix_gh, atol=1e-14)
+        True
+
+        Notes
+        -----
+        .. versionadded:: 1.8.0
+
+        In each row of the design matrix all the basis elements are evaluated
+        at the certain point (first row - x[0], ..., last row - x[-1]).
+
+        `nt` is a length of the vector of knots: as far as there are
+        `nt - k - 1` basis elements, `nt` should be not less than `2 * k + 2`
+        to have at least `k + 1` basis element.
+
+        Out of bounds `x` raises a ValueError.
+        """
+        x = _as_float_array(x, True)
+        t = _as_float_array(t, True)
+
+        if extrapolate != 'periodic':
+            extrapolate = bool(extrapolate)
+
+        if k < 0:
+            raise ValueError("Spline order cannot be negative.")
+        if t.ndim != 1 or np.any(t[1:] < t[:-1]):
+            raise ValueError(f"Expect t to be a 1-D sorted array_like, but "
+                             f"got t={t}.")
+        # There are `nt - k - 1` basis elements in a BSpline built on the
+        # vector of knots with length `nt`, so to have at least `k + 1` basis
+        # elements we need to have at least `2 * k + 2` elements in the vector
+        # of knots.
+        if len(t) < 2 * k + 2:
+            raise ValueError(f"Length t is not enough for k={k}.")
+
+        if extrapolate == 'periodic':
+            # With periodic extrapolation we map x to the segment
+            # [t[k], t[n]].
+            n = t.size - k - 1
+            x = t[k] + (x - t[k]) % (t[n] - t[k])
+            extrapolate = False
+        elif not extrapolate and (
+            (min(x) < t[k]) or (max(x) > t[t.shape[0] - k - 1])
+        ):
+            # Checks from `find_interval` function
+            raise ValueError(f'Out of bounds w/ x = {x}.')
+
+        # Compute number of non-zeros of final CSR array in order to determine
+        # the dtype of indices and indptr of the CSR array.
+        n = x.shape[0]
+        nnz = n * (k + 1)
+        if nnz < np.iinfo(np.int32).max:
+            int_dtype = np.int32
+        else:
+            int_dtype = np.int64
+        # Preallocate indptr and indices
+        indices = np.empty(n * (k + 1), dtype=int_dtype)
+        indptr = np.arange(0, (n + 1) * (k + 1), k + 1, dtype=int_dtype)
+
+        # indptr is not passed to Cython as it is already fully computed
+        data, indices = _bspl._make_design_matrix(
+            x, t, k, extrapolate, indices
+        )
+        return csr_array(
+            (data, indices, indptr),
+            shape=(x.shape[0], t.shape[0] - k - 1)
+        )
+
+    def __call__(self, x, nu=0, extrapolate=None):
+        """
+        Evaluate a spline function.
+
+        Parameters
+        ----------
+        x : array_like
+            points to evaluate the spline at.
+        nu : int, optional
+            derivative to evaluate (default is 0).
+        extrapolate : bool or 'periodic', optional
+            whether to extrapolate based on the first and last intervals
+            or return nans. If 'periodic', periodic extrapolation is used.
+            Default is `self.extrapolate`.
+
+        Returns
+        -------
+        y : array_like
+            Shape is determined by replacing the interpolation axis
+            in the coefficient array with the shape of `x`.
+
+        """
+        if extrapolate is None:
+            extrapolate = self.extrapolate
+        x = np.asarray(x)
+        x_shape, x_ndim = x.shape, x.ndim
+        x = np.ascontiguousarray(x.ravel(), dtype=np.float64)
+
+        # With periodic extrapolation we map x to the segment
+        # [self.t[k], self.t[n]].
+        if extrapolate == 'periodic':
+            n = self.t.size - self.k - 1
+            x = self.t[self.k] + (x - self.t[self.k]) % (self.t[n] -
+                                                         self.t[self.k])
+            extrapolate = False
+
+        out = np.empty((len(x), prod(self.c.shape[1:])), dtype=self.c.dtype)
+        self._ensure_c_contiguous()
+        self._evaluate(x, nu, extrapolate, out)
+        out = out.reshape(x_shape + self.c.shape[1:])
+        if self.axis != 0:
+            # transpose to move the calculated values to the interpolation axis
+            l = list(range(out.ndim))
+            l = l[x_ndim:x_ndim+self.axis] + l[:x_ndim] + l[x_ndim+self.axis:]
+            out = out.transpose(l)
+        return out
+
+    def _evaluate(self, xp, nu, extrapolate, out):
+        _bspl.evaluate_spline(self.t, self.c.reshape(self.c.shape[0], -1),
+                              self.k, xp, nu, extrapolate, out)
+
+    def _ensure_c_contiguous(self):
+        """
+        c and t may be modified by the user. The Cython code expects
+        that they are C contiguous.
+
+        """
+        if not self.t.flags.c_contiguous:
+            self.t = self.t.copy()
+        if not self.c.flags.c_contiguous:
+            self.c = self.c.copy()
+
+    def derivative(self, nu=1):
+        """Return a B-spline representing the derivative.
+
+        Parameters
+        ----------
+        nu : int, optional
+            Derivative order.
+            Default is 1.
+
+        Returns
+        -------
+        b : BSpline object
+            A new instance representing the derivative.
+
+        See Also
+        --------
+        splder, splantider
+
+        """
+        c = self.c
+        # pad the c array if needed
+        ct = len(self.t) - len(c)
+        if ct > 0:
+            c = np.r_[c, np.zeros((ct,) + c.shape[1:])]
+        tck = _fitpack_impl.splder((self.t, c, self.k), nu)
+        return self.construct_fast(*tck, extrapolate=self.extrapolate,
+                                   axis=self.axis)
+
+    def antiderivative(self, nu=1):
+        """Return a B-spline representing the antiderivative.
+
+        Parameters
+        ----------
+        nu : int, optional
+            Antiderivative order. Default is 1.
+
+        Returns
+        -------
+        b : BSpline object
+            A new instance representing the antiderivative.
+
+        Notes
+        -----
+        If antiderivative is computed and ``self.extrapolate='periodic'``,
+        it will be set to False for the returned instance. This is done because
+        the antiderivative is no longer periodic and its correct evaluation
+        outside of the initially given x interval is difficult.
+
+        See Also
+        --------
+        splder, splantider
+
+        """
+        c = self.c
+        # pad the c array if needed
+        ct = len(self.t) - len(c)
+        if ct > 0:
+            c = np.r_[c, np.zeros((ct,) + c.shape[1:])]
+        tck = _fitpack_impl.splantider((self.t, c, self.k), nu)
+
+        if self.extrapolate == 'periodic':
+            extrapolate = False
+        else:
+            extrapolate = self.extrapolate
+
+        return self.construct_fast(*tck, extrapolate=extrapolate,
+                                   axis=self.axis)
+
+    def integrate(self, a, b, extrapolate=None):
+        """Compute a definite integral of the spline.
+
+        Parameters
+        ----------
+        a : float
+            Lower limit of integration.
+        b : float
+            Upper limit of integration.
+        extrapolate : bool or 'periodic', optional
+            whether to extrapolate beyond the base interval,
+            ``t[k] .. t[-k-1]``, or take the spline to be zero outside of the
+            base interval. If 'periodic', periodic extrapolation is used.
+            If None (default), use `self.extrapolate`.
+
+        Returns
+        -------
+        I : array_like
+            Definite integral of the spline over the interval ``[a, b]``.
+
+        Examples
+        --------
+        Construct the linear spline ``x if x < 1 else 2 - x`` on the base
+        interval :math:`[0, 2]`, and integrate it
+
+        >>> from scipy.interpolate import BSpline
+        >>> b = BSpline.basis_element([0, 1, 2])
+        >>> b.integrate(0, 1)
+        array(0.5)
+
+        If the integration limits are outside of the base interval, the result
+        is controlled by the `extrapolate` parameter
+
+        >>> b.integrate(-1, 1)
+        array(0.0)
+        >>> b.integrate(-1, 1, extrapolate=False)
+        array(0.5)
+
+        >>> import matplotlib.pyplot as plt
+        >>> fig, ax = plt.subplots()
+        >>> ax.grid(True)
+        >>> ax.axvline(0, c='r', lw=5, alpha=0.5)  # base interval
+        >>> ax.axvline(2, c='r', lw=5, alpha=0.5)
+        >>> xx = [-1, 1, 2]
+        >>> ax.plot(xx, b(xx))
+        >>> plt.show()
+
+        """
+        if extrapolate is None:
+            extrapolate = self.extrapolate
+
+        # Prepare self.t and self.c.
+        self._ensure_c_contiguous()
+
+        # Swap integration bounds if needed.
+        sign = 1
+        if b < a:
+            a, b = b, a
+            sign = -1
+        n = self.t.size - self.k - 1
+
+        if extrapolate != "periodic" and not extrapolate:
+            # Shrink the integration interval, if needed.
+            a = max(a, self.t[self.k])
+            b = min(b, self.t[n])
+
+            if self.c.ndim == 1:
+                # Fast path: use FITPACK's routine
+                # (cf _fitpack_impl.splint).
+                integral = _fitpack_impl.splint(a, b, self.tck)
+                return integral * sign
+
+        out = np.empty((2, prod(self.c.shape[1:])), dtype=self.c.dtype)
+
+        # Compute the antiderivative.
+        c = self.c
+        ct = len(self.t) - len(c)
+        if ct > 0:
+            c = np.r_[c, np.zeros((ct,) + c.shape[1:])]
+        ta, ca, ka = _fitpack_impl.splantider((self.t, c, self.k), 1)
+
+        if extrapolate == 'periodic':
+            # Split the integral into the part over period (can be several
+            # of them) and the remaining part.
+
+            ts, te = self.t[self.k], self.t[n]
+            period = te - ts
+            interval = b - a
+            n_periods, left = divmod(interval, period)
+
+            if n_periods > 0:
+                # Evaluate the difference of antiderivatives.
+                x = np.asarray([ts, te], dtype=np.float64)
+                _bspl.evaluate_spline(ta, ca.reshape(ca.shape[0], -1),
+                                      ka, x, 0, False, out)
+                integral = out[1] - out[0]
+                integral *= n_periods
+            else:
+                integral = np.zeros((1, prod(self.c.shape[1:])),
+                                    dtype=self.c.dtype)
+
+            # Map a to [ts, te], b is always a + left.
+            a = ts + (a - ts) % period
+            b = a + left
+
+            # If b <= te then we need to integrate over [a, b], otherwise
+            # over [a, te] and from xs to what is remained.
+            if b <= te:
+                x = np.asarray([a, b], dtype=np.float64)
+                _bspl.evaluate_spline(ta, ca.reshape(ca.shape[0], -1),
+                                      ka, x, 0, False, out)
+                integral += out[1] - out[0]
+            else:
+                x = np.asarray([a, te], dtype=np.float64)
+                _bspl.evaluate_spline(ta, ca.reshape(ca.shape[0], -1),
+                                      ka, x, 0, False, out)
+                integral += out[1] - out[0]
+
+                x = np.asarray([ts, ts + b - te], dtype=np.float64)
+                _bspl.evaluate_spline(ta, ca.reshape(ca.shape[0], -1),
+                                      ka, x, 0, False, out)
+                integral += out[1] - out[0]
+        else:
+            # Evaluate the difference of antiderivatives.
+            x = np.asarray([a, b], dtype=np.float64)
+            _bspl.evaluate_spline(ta, ca.reshape(ca.shape[0], -1),
+                                  ka, x, 0, extrapolate, out)
+            integral = out[1] - out[0]
+
+        integral *= sign
+        return integral.reshape(ca.shape[1:])
+
+    @classmethod
+    def from_power_basis(cls, pp, bc_type='not-a-knot'):
+        r"""
+        Construct a polynomial in the B-spline basis
+        from a piecewise polynomial in the power basis.
+
+        For now, accepts ``CubicSpline`` instances only.
+
+        Parameters
+        ----------
+        pp : CubicSpline
+            A piecewise polynomial in the power basis, as created
+            by ``CubicSpline``
+        bc_type : string, optional
+            Boundary condition type as in ``CubicSpline``: one of the
+            ``not-a-knot``, ``natural``, ``clamped``, or ``periodic``.
+            Necessary for construction an instance of ``BSpline`` class.
+            Default is ``not-a-knot``.
+
+        Returns
+        -------
+        b : BSpline object
+            A new instance representing the initial polynomial
+            in the B-spline basis.
+
+        Notes
+        -----
+        .. versionadded:: 1.8.0
+
+        Accepts only ``CubicSpline`` instances for now.
+
+        The algorithm follows from differentiation
+        the Marsden's identity [1]: each of coefficients of spline
+        interpolation function in the B-spline basis is computed as follows:
+
+        .. math::
+
+            c_j = \sum_{m=0}^{k} \frac{(k-m)!}{k!}
+                       c_{m,i} (-1)^{k-m} D^m p_{j,k}(x_i)
+
+        :math:`c_{m, i}` - a coefficient of CubicSpline,
+        :math:`D^m p_{j, k}(x_i)` - an m-th defivative of a dual polynomial
+        in :math:`x_i`.
+
+        ``k`` always equals 3 for now.
+
+        First ``n - 2`` coefficients are computed in :math:`x_i = x_j`, e.g.
+
+        .. math::
+
+            c_1 = \sum_{m=0}^{k} \frac{(k-1)!}{k!} c_{m,1} D^m p_{j,3}(x_1)
+
+        Last ``nod + 2`` coefficients are computed in ``x[-2]``,
+        ``nod`` - number of derivatives at the ends.
+
+        For example, consider :math:`x = [0, 1, 2, 3, 4]`,
+        :math:`y = [1, 1, 1, 1, 1]` and bc_type = ``natural``
+
+        The coefficients of CubicSpline in the power basis:
+
+        :math:`[[0, 0, 0, 0, 0], [0, 0, 0, 0, 0],
+        [0, 0, 0, 0, 0], [1, 1, 1, 1, 1]]`
+
+        The knot vector: :math:`t = [0, 0, 0, 0, 1, 2, 3, 4, 4, 4, 4]`
+
+        In this case
+
+        .. math::
+
+            c_j = \frac{0!}{k!} c_{3, i} k! = c_{3, i} = 1,~j = 0, ..., 6
+
+        References
+        ----------
+        .. [1] Tom Lyche and Knut Morken, Spline Methods, 2005, Section 3.1.2
+
+        """
+        from ._cubic import CubicSpline
+        if not isinstance(pp, CubicSpline):
+            raise NotImplementedError("Only CubicSpline objects are accepted"
+                                      "for now. Got %s instead." % type(pp))
+        x = pp.x
+        coef = pp.c
+        k = pp.c.shape[0] - 1
+        n = x.shape[0]
+
+        if bc_type == 'not-a-knot':
+            t = _not_a_knot(x, k)
+        elif bc_type == 'natural' or bc_type == 'clamped':
+            t = _augknt(x, k)
+        elif bc_type == 'periodic':
+            t = _periodic_knots(x, k)
+        else:
+            raise TypeError('Unknown boundary condition: %s' % bc_type)
+
+        nod = t.shape[0] - (n + k + 1)  # number of derivatives at the ends
+        c = np.zeros(n + nod, dtype=pp.c.dtype)
+        for m in range(k + 1):
+            for i in range(n - 2):
+                c[i] += poch(k + 1, -m) * coef[m, i]\
+                        * np.power(-1, k - m)\
+                        * _diff_dual_poly(i, k, x[i], m, t)
+            for j in range(n - 2, n + nod):
+                c[j] += poch(k + 1, -m) * coef[m, n - 2]\
+                        * np.power(-1, k - m)\
+                        * _diff_dual_poly(j, k, x[n - 2], m, t)
+        return cls.construct_fast(t, c, k, pp.extrapolate, pp.axis)
+
+    def insert_knot(self, x, m=1):
+        """Insert a new knot at `x` of multiplicity `m`.
+
+        Given the knots and coefficients of a B-spline representation, create a
+        new B-spline with a knot inserted `m` times at point `x`.
+
+        Parameters
+        ----------
+        x : float
+            The position of the new knot
+        m : int, optional
+            The number of times to insert the given knot (its multiplicity).
+            Default is 1.
+
+        Returns
+        -------
+        spl : BSpline object
+            A new BSpline object with the new knot inserted.
+
+        Notes
+        -----
+        Based on algorithms from [1]_ and [2]_.
+
+        In case of a periodic spline (``self.extrapolate == "periodic"``)
+        there must be either at least k interior knots t(j) satisfying
+        ``t(k+1)<t(j)<=x`` or at least k interior knots t(j) satisfying
+        ``x<=t(j)<t(n-k)``.
+
+        This routine is functionally equivalent to `scipy.interpolate.insert`.
+
+        .. versionadded:: 1.13
+
+        References
+        ----------
+        .. [1] W. Boehm, "Inserting new knots into b-spline curves.",
+            Computer Aided Design, 12, p.199-201, 1980.
+            :doi:`10.1016/0010-4485(80)90154-2`.
+        .. [2] P. Dierckx, "Curve and surface fitting with splines, Monographs on
+            Numerical Analysis", Oxford University Press, 1993.
+
+        See Also
+        --------
+        scipy.interpolate.insert
+
+        Examples
+        --------
+        You can insert knots into a B-spline:
+
+        >>> import numpy as np
+        >>> from scipy.interpolate import BSpline, make_interp_spline
+        >>> x = np.linspace(0, 10, 5)
+        >>> y = np.sin(x)
+        >>> spl = make_interp_spline(x, y, k=3)
+        >>> spl.t
+        array([ 0.,  0.,  0.,  0.,  5., 10., 10., 10., 10.])
+
+        Insert a single knot
+
+        >>> spl_1 = spl.insert_knot(3)
+        >>> spl_1.t
+        array([ 0.,  0.,  0.,  0.,  3.,  5., 10., 10., 10., 10.])
+
+        Insert a multiple knot
+
+        >>> spl_2 = spl.insert_knot(8, m=3)
+        >>> spl_2.t
+        array([ 0.,  0.,  0.,  0.,  5.,  8.,  8.,  8., 10., 10., 10., 10.])
+
+        """
+        if x < self.t[self.k] or x > self.t[-self.k-1]:
+            raise ValueError(f"Cannot insert a knot at {x}.")
+        if m <= 0:
+            raise ValueError(f"`m` must be positive, got {m = }.")
+
+        extradim = self.c.shape[1:]
+        num_extra = prod(extradim)
+
+        tt = self.t.copy()
+        cc = self.c.copy()
+        cc = cc.reshape(-1, num_extra)
+
+        for _ in range(m):
+            tt, cc = _bspl.insert(x, tt, cc, self.k, self.extrapolate == "periodic")
+
+        return self.construct_fast(
+            tt, cc.reshape((-1,) + extradim), self.k, self.extrapolate, self.axis
+        )
+
+
+#################################
+#  Interpolating spline helpers #
+#################################
+
+def _not_a_knot(x, k):
+    """Given data x, construct the knot vector w/ not-a-knot BC.
+    cf de Boor, XIII(12)."""
+    x = np.asarray(x)
+    if k % 2 != 1:
+        raise ValueError("Odd degree for now only. Got %s." % k)
+
+    m = (k - 1) // 2
+    t = x[m+1:-m-1]
+    t = np.r_[(x[0],)*(k+1), t, (x[-1],)*(k+1)]
+    return t
+
+
+def _augknt(x, k):
+    """Construct a knot vector appropriate for the order-k interpolation."""
+    return np.r_[(x[0],)*k, x, (x[-1],)*k]
+
+
+def _convert_string_aliases(deriv, target_shape):
+    if isinstance(deriv, str):
+        if deriv == "clamped":
+            deriv = [(1, np.zeros(target_shape))]
+        elif deriv == "natural":
+            deriv = [(2, np.zeros(target_shape))]
+        else:
+            raise ValueError("Unknown boundary condition : %s" % deriv)
+    return deriv
+
+
+def _process_deriv_spec(deriv):
+    if deriv is not None:
+        try:
+            ords, vals = zip(*deriv)
+        except TypeError as e:
+            msg = ("Derivatives, `bc_type`, should be specified as a pair of "
+                   "iterables of pairs of (order, value).")
+            raise ValueError(msg) from e
+    else:
+        ords, vals = [], []
+    return np.atleast_1d(ords, vals)
+
+
+def _woodbury_algorithm(A, ur, ll, b, k):
+    '''
+    Solve a cyclic banded linear system with upper right
+    and lower blocks of size ``(k-1) / 2`` using
+    the Woodbury formula
+
+    Parameters
+    ----------
+    A : 2-D array, shape(k, n)
+        Matrix of diagonals of original matrix (see
+        ``solve_banded`` documentation).
+    ur : 2-D array, shape(bs, bs)
+        Upper right block matrix.
+    ll : 2-D array, shape(bs, bs)
+        Lower left block matrix.
+    b : 1-D array, shape(n,)
+        Vector of constant terms of the system of linear equations.
+    k : int
+        B-spline degree.
+
+    Returns
+    -------
+    c : 1-D array, shape(n,)
+        Solution of the original system of linear equations.
+
+    Notes
+    -----
+    This algorithm works only for systems with banded matrix A plus
+    a correction term U @ V.T, where the matrix U @ V.T gives upper right
+    and lower left block of A
+    The system is solved with the following steps:
+        1.  New systems of linear equations are constructed:
+            A @ z_i = u_i,
+            u_i - column vector of U,
+            i = 1, ..., k - 1
+        2.  Matrix Z is formed from vectors z_i:
+            Z = [ z_1 | z_2 | ... | z_{k - 1} ]
+        3.  Matrix H = (1 + V.T @ Z)^{-1}
+        4.  The system A' @ y = b is solved
+        5.  x = y - Z @ (H @ V.T @ y)
+    Also, ``n`` should be greater than ``k``, otherwise corner block
+    elements will intersect with diagonals.
+
+    Examples
+    --------
+    Consider the case of n = 8, k = 5 (size of blocks - 2 x 2).
+    The matrix of a system:       U:          V:
+      x  x  x  *  *  a  b         a b 0 0     0 0 1 0
+      x  x  x  x  *  *  c         0 c 0 0     0 0 0 1
+      x  x  x  x  x  *  *         0 0 0 0     0 0 0 0
+      *  x  x  x  x  x  *         0 0 0 0     0 0 0 0
+      *  *  x  x  x  x  x         0 0 0 0     0 0 0 0
+      d  *  *  x  x  x  x         0 0 d 0     1 0 0 0
+      e  f  *  *  x  x  x         0 0 e f     0 1 0 0
+
+    References
+    ----------
+    .. [1] William H. Press, Saul A. Teukolsky, William T. Vetterling
+           and Brian P. Flannery, Numerical Recipes, 2007, Section 2.7.3
+
+    '''
+    k_mod = k - k % 2
+    bs = int((k - 1) / 2) + (k + 1) % 2
+
+    n = A.shape[1] + 1
+    U = np.zeros((n - 1, k_mod))
+    VT = np.zeros((k_mod, n - 1))  # V transpose
+
+    # upper right block
+    U[:bs, :bs] = ur
+    VT[np.arange(bs), np.arange(bs) - bs] = 1
+
+    # lower left block
+    U[-bs:, -bs:] = ll
+    VT[np.arange(bs) - bs, np.arange(bs)] = 1
+
+    Z = solve_banded((bs, bs), A, U)
+
+    H = solve(np.identity(k_mod) + VT @ Z, np.identity(k_mod))
+
+    y = solve_banded((bs, bs), A, b)
+    c = y - Z @ (H @ (VT @ y))
+
+    return c
+
+
+def _periodic_knots(x, k):
+    '''
+    returns vector of nodes on circle
+    '''
+    xc = np.copy(x)
+    n = len(xc)
+    if k % 2 == 0:
+        dx = np.diff(xc)
+        xc[1: -1] -= dx[:-1] / 2
+    dx = np.diff(xc)
+    t = np.zeros(n + 2 * k)
+    t[k: -k] = xc
+    for i in range(0, k):
+        # filling first `k` elements in descending order
+        t[k - i - 1] = t[k - i] - dx[-(i % (n - 1)) - 1]
+        # filling last `k` elements in ascending order
+        t[-k + i] = t[-k + i - 1] + dx[i % (n - 1)]
+    return t
+
+
+def _make_interp_per_full_matr(x, y, t, k):
+    '''
+    Returns a solution of a system for B-spline interpolation with periodic
+    boundary conditions. First ``k - 1`` rows of matrix are conditions of
+    periodicity (continuity of ``k - 1`` derivatives at the boundary points).
+    Last ``n`` rows are interpolation conditions.
+    RHS is ``k - 1`` zeros and ``n`` ordinates in this case.
+
+    Parameters
+    ----------
+    x : 1-D array, shape (n,)
+        Values of x - coordinate of a given set of points.
+    y : 1-D array, shape (n,)
+        Values of y - coordinate of a given set of points.
+    t : 1-D array, shape(n+2*k,)
+        Vector of knots.
+    k : int
+        The maximum degree of spline
+
+    Returns
+    -------
+    c : 1-D array, shape (n+k-1,)
+        B-spline coefficients
+
+    Notes
+    -----
+    ``t`` is supposed to be taken on circle.
+
+    '''
+
+    x, y, t = map(np.asarray, (x, y, t))
+
+    n = x.size
+    # LHS: the collocation matrix + derivatives at edges
+    matr = np.zeros((n + k - 1, n + k - 1))
+
+    # derivatives at x[0] and x[-1]:
+    for i in range(k - 1):
+        bb = _bspl.evaluate_all_bspl(t, k, x[0], k, nu=i + 1)
+        matr[i, : k + 1] += bb
+        bb = _bspl.evaluate_all_bspl(t, k, x[-1], n + k - 1, nu=i + 1)[:-1]
+        matr[i, -k:] -= bb
+
+    # collocation matrix
+    for i in range(n):
+        xval = x[i]
+        # find interval
+        if xval == t[k]:
+            left = k
+        else:
+            left = np.searchsorted(t, xval) - 1
+
+        # fill a row
+        bb = _bspl.evaluate_all_bspl(t, k, xval, left)
+        matr[i + k - 1, left-k:left+1] = bb
+
+    # RHS
+    b = np.r_[[0] * (k - 1), y]
+
+    c = solve(matr, b)
+    return c
+
+
+def _make_periodic_spline(x, y, t, k, axis):
+    '''
+    Compute the (coefficients of) interpolating B-spline with periodic
+    boundary conditions.
+
+    Parameters
+    ----------
+    x : array_like, shape (n,)
+        Abscissas.
+    y : array_like, shape (n,)
+        Ordinates.
+    k : int
+        B-spline degree.
+    t : array_like, shape (n + 2 * k,).
+        Knots taken on a circle, ``k`` on the left and ``k`` on the right
+        of the vector ``x``.
+
+    Returns
+    -------
+    b : a BSpline object of the degree ``k`` and with knots ``t``.
+
+    Notes
+    -----
+    The original system is formed by ``n + k - 1`` equations where the first
+    ``k - 1`` of them stand for the ``k - 1`` derivatives continuity on the
+    edges while the other equations correspond to an interpolating case
+    (matching all the input points). Due to a special form of knot vector, it
+    can be proved that in the original system the first and last ``k``
+    coefficients of a spline function are the same, respectively. It follows
+    from the fact that all ``k - 1`` derivatives are equal term by term at ends
+    and that the matrix of the original system of linear equations is
+    non-degenerate. So, we can reduce the number of equations to ``n - 1``
+    (first ``k - 1`` equations could be reduced). Another trick of this
+    implementation is cyclic shift of values of B-splines due to equality of
+    ``k`` unknown coefficients. With this we can receive matrix of the system
+    with upper right and lower left blocks, and ``k`` diagonals.  It allows
+    to use Woodbury formula to optimize the computations.
+
+    '''
+    n = y.shape[0]
+
+    extradim = prod(y.shape[1:])
+    y_new = y.reshape(n, extradim)
+    c = np.zeros((n + k - 1, extradim))
+
+    # n <= k case is solved with full matrix
+    if n <= k:
+        for i in range(extradim):
+            c[:, i] = _make_interp_per_full_matr(x, y_new[:, i], t, k)
+        c = np.ascontiguousarray(c.reshape((n + k - 1,) + y.shape[1:]))
+        return BSpline.construct_fast(t, c, k, extrapolate='periodic', axis=axis)
+
+    nt = len(t) - k - 1
+
+    # size of block elements
+    kul = int(k / 2)
+
+    # kl = ku = k
+    ab = np.zeros((3 * k + 1, nt), dtype=np.float64, order='F')
+
+    # upper right and lower left blocks
+    ur = np.zeros((kul, kul))
+    ll = np.zeros_like(ur)
+
+    # `offset` is made to shift all the non-zero elements to the end of the
+    # matrix
+    _bspl._colloc(x, t, k, ab, offset=k)
+
+    # remove zeros before the matrix
+    ab = ab[-k - (k + 1) % 2:, :]
+
+    # The least elements in rows (except repetitions) are diagonals
+    # of block matrices. Upper right matrix is an upper triangular
+    # matrix while lower left is a lower triangular one.
+    for i in range(kul):
+        ur += np.diag(ab[-i - 1, i: kul], k=i)
+        ll += np.diag(ab[i, -kul - (k % 2): n - 1 + 2 * kul - i], k=-i)
+
+    # remove elements that occur in the last point
+    # (first and last points are equivalent)
+    A = ab[:, kul: -k + kul]
+
+    for i in range(extradim):
+        cc = _woodbury_algorithm(A, ur, ll, y_new[:, i][:-1], k)
+        c[:, i] = np.concatenate((cc[-kul:], cc, cc[:kul + k % 2]))
+    c = np.ascontiguousarray(c.reshape((n + k - 1,) + y.shape[1:]))
+    return BSpline.construct_fast(t, c, k, extrapolate='periodic', axis=axis)
+
+
+def make_interp_spline(x, y, k=3, t=None, bc_type=None, axis=0,
+                       check_finite=True):
+    """Compute the (coefficients of) interpolating B-spline.
+
+    Parameters
+    ----------
+    x : array_like, shape (n,)
+        Abscissas.
+    y : array_like, shape (n, ...)
+        Ordinates.
+    k : int, optional
+        B-spline degree. Default is cubic, ``k = 3``.
+    t : array_like, shape (nt + k + 1,), optional.
+        Knots.
+        The number of knots needs to agree with the number of data points and
+        the number of derivatives at the edges. Specifically, ``nt - n`` must
+        equal ``len(deriv_l) + len(deriv_r)``.
+    bc_type : 2-tuple or None
+        Boundary conditions.
+        Default is None, which means choosing the boundary conditions
+        automatically. Otherwise, it must be a length-two tuple where the first
+        element (``deriv_l``) sets the boundary conditions at ``x[0]`` and
+        the second element (``deriv_r``) sets the boundary conditions at
+        ``x[-1]``. Each of these must be an iterable of pairs
+        ``(order, value)`` which gives the values of derivatives of specified
+        orders at the given edge of the interpolation interval.
+        Alternatively, the following string aliases are recognized:
+
+        * ``"clamped"``: The first derivatives at the ends are zero. This is
+           equivalent to ``bc_type=([(1, 0.0)], [(1, 0.0)])``.
+        * ``"natural"``: The second derivatives at ends are zero. This is
+          equivalent to ``bc_type=([(2, 0.0)], [(2, 0.0)])``.
+        * ``"not-a-knot"`` (default): The first and second segments are the
+          same polynomial. This is equivalent to having ``bc_type=None``.
+        * ``"periodic"``: The values and the first ``k-1`` derivatives at the
+          ends are equivalent.
+
+    axis : int, optional
+        Interpolation axis. Default is 0.
+    check_finite : bool, optional
+        Whether to check that the input arrays contain only finite numbers.
+        Disabling may give a performance gain, but may result in problems
+        (crashes, non-termination) if the inputs do contain infinities or NaNs.
+        Default is True.
+
+    Returns
+    -------
+    b : a BSpline object of the degree ``k`` and with knots ``t``.
+
+    See Also
+    --------
+    BSpline : base class representing the B-spline objects
+    CubicSpline : a cubic spline in the polynomial basis
+    make_lsq_spline : a similar factory function for spline fitting
+    UnivariateSpline : a wrapper over FITPACK spline fitting routines
+    splrep : a wrapper over FITPACK spline fitting routines
+
+    Examples
+    --------
+
+    Use cubic interpolation on Chebyshev nodes:
+
+    >>> import numpy as np
+    >>> import matplotlib.pyplot as plt
+    >>> def cheb_nodes(N):
+    ...     jj = 2.*np.arange(N) + 1
+    ...     x = np.cos(np.pi * jj / 2 / N)[::-1]
+    ...     return x
+
+    >>> x = cheb_nodes(20)
+    >>> y = np.sqrt(1 - x**2)
+
+    >>> from scipy.interpolate import BSpline, make_interp_spline
+    >>> b = make_interp_spline(x, y)
+    >>> np.allclose(b(x), y)
+    True
+
+    Note that the default is a cubic spline with a not-a-knot boundary condition
+
+    >>> b.k
+    3
+
+    Here we use a 'natural' spline, with zero 2nd derivatives at edges:
+
+    >>> l, r = [(2, 0.0)], [(2, 0.0)]
+    >>> b_n = make_interp_spline(x, y, bc_type=(l, r))  # or, bc_type="natural"
+    >>> np.allclose(b_n(x), y)
+    True
+    >>> x0, x1 = x[0], x[-1]
+    >>> np.allclose([b_n(x0, 2), b_n(x1, 2)], [0, 0])
+    True
+
+    Interpolation of parametric curves is also supported. As an example, we
+    compute a discretization of a snail curve in polar coordinates
+
+    >>> phi = np.linspace(0, 2.*np.pi, 40)
+    >>> r = 0.3 + np.cos(phi)
+    >>> x, y = r*np.cos(phi), r*np.sin(phi)  # convert to Cartesian coordinates
+
+    Build an interpolating curve, parameterizing it by the angle
+
+    >>> spl = make_interp_spline(phi, np.c_[x, y])
+
+    Evaluate the interpolant on a finer grid (note that we transpose the result
+    to unpack it into a pair of x- and y-arrays)
+
+    >>> phi_new = np.linspace(0, 2.*np.pi, 100)
+    >>> x_new, y_new = spl(phi_new).T
+
+    Plot the result
+
+    >>> plt.plot(x, y, 'o')
+    >>> plt.plot(x_new, y_new, '-')
+    >>> plt.show()
+
+    Build a B-spline curve with 2 dimensional y
+
+    >>> x = np.linspace(0, 2*np.pi, 10)
+    >>> y = np.array([np.sin(x), np.cos(x)])
+
+    Periodic condition is satisfied because y coordinates of points on the ends
+    are equivalent
+
+    >>> ax = plt.axes(projection='3d')
+    >>> xx = np.linspace(0, 2*np.pi, 100)
+    >>> bspl = make_interp_spline(x, y, k=5, bc_type='periodic', axis=1)
+    >>> ax.plot3D(xx, *bspl(xx))
+    >>> ax.scatter3D(x, *y, color='red')
+    >>> plt.show()
+
+    """
+    # convert string aliases for the boundary conditions
+    if bc_type is None or bc_type == 'not-a-knot' or bc_type == 'periodic':
+        deriv_l, deriv_r = None, None
+    elif isinstance(bc_type, str):
+        deriv_l, deriv_r = bc_type, bc_type
+    else:
+        try:
+            deriv_l, deriv_r = bc_type
+        except TypeError as e:
+            raise ValueError("Unknown boundary condition: %s" % bc_type) from e
+
+    y = np.asarray(y)
+
+    axis = normalize_axis_index(axis, y.ndim)
+
+    x = _as_float_array(x, check_finite)
+    y = _as_float_array(y, check_finite)
+
+    y = np.moveaxis(y, axis, 0)    # now internally interp axis is zero
+
+    # sanity check the input
+    if bc_type == 'periodic' and not np.allclose(y[0], y[-1], atol=1e-15):
+        raise ValueError("First and last points does not match while "
+                         "periodic case expected")
+    if x.size != y.shape[0]:
+        raise ValueError(f'Shapes of x {x.shape} and y {y.shape} are incompatible')
+    if np.any(x[1:] == x[:-1]):
+        raise ValueError("Expect x to not have duplicates")
+    if x.ndim != 1 or np.any(x[1:] < x[:-1]):
+        raise ValueError("Expect x to be a 1D strictly increasing sequence.")
+
+    # special-case k=0 right away
+    if k == 0:
+        if any(_ is not None for _ in (t, deriv_l, deriv_r)):
+            raise ValueError("Too much info for k=0: t and bc_type can only "
+                             "be None.")
+        t = np.r_[x, x[-1]]
+        c = np.asarray(y)
+        c = np.ascontiguousarray(c, dtype=_get_dtype(c.dtype))
+        return BSpline.construct_fast(t, c, k, axis=axis)
+
+    # special-case k=1 (e.g., Lyche and Morken, Eq.(2.16))
+    if k == 1 and t is None:
+        if not (deriv_l is None and deriv_r is None):
+            raise ValueError("Too much info for k=1: bc_type can only be None.")
+        t = np.r_[x[0], x, x[-1]]
+        c = np.asarray(y)
+        c = np.ascontiguousarray(c, dtype=_get_dtype(c.dtype))
+        return BSpline.construct_fast(t, c, k, axis=axis)
+
+    k = operator.index(k)
+
+    if bc_type == 'periodic' and t is not None:
+        raise NotImplementedError("For periodic case t is constructed "
+                                  "automatically and can not be passed "
+                                  "manually")
+
+    # come up with a sensible knot vector, if needed
+    if t is None:
+        if deriv_l is None and deriv_r is None:
+            if bc_type == 'periodic':
+                t = _periodic_knots(x, k)
+            elif k == 2:
+                # OK, it's a bit ad hoc: Greville sites + omit
+                # 2nd and 2nd-to-last points, a la not-a-knot
+                t = (x[1:] + x[:-1]) / 2.
+                t = np.r_[(x[0],)*(k+1),
+                          t[1:-1],
+                          (x[-1],)*(k+1)]
+            else:
+                t = _not_a_knot(x, k)
+        else:
+            t = _augknt(x, k)
+
+    t = _as_float_array(t, check_finite)
+
+    if k < 0:
+        raise ValueError("Expect non-negative k.")
+    if t.ndim != 1 or np.any(t[1:] < t[:-1]):
+        raise ValueError("Expect t to be a 1-D sorted array_like.")
+    if t.size < x.size + k + 1:
+        raise ValueError('Got %d knots, need at least %d.' %
+                         (t.size, x.size + k + 1))
+    if (x[0] < t[k]) or (x[-1] > t[-k]):
+        raise ValueError('Out of bounds w/ x = %s.' % x)
+
+    if bc_type == 'periodic':
+        return _make_periodic_spline(x, y, t, k, axis)
+
+    # Here : deriv_l, r = [(nu, value), ...]
+    deriv_l = _convert_string_aliases(deriv_l, y.shape[1:])
+    deriv_l_ords, deriv_l_vals = _process_deriv_spec(deriv_l)
+    nleft = deriv_l_ords.shape[0]
+
+    deriv_r = _convert_string_aliases(deriv_r, y.shape[1:])
+    deriv_r_ords, deriv_r_vals = _process_deriv_spec(deriv_r)
+    nright = deriv_r_ords.shape[0]
+
+    # have `n` conditions for `nt` coefficients; need nt-n derivatives
+    n = x.size
+    nt = t.size - k - 1
+
+    if nt - n != nleft + nright:
+        raise ValueError("The number of derivatives at boundaries does not "
+                         f"match: expected {nt-n}, got {nleft}+{nright}")
+
+    # bail out if the `y` array is zero-sized
+    if y.size == 0:
+        c = np.zeros((nt,) + y.shape[1:], dtype=float)
+        return BSpline.construct_fast(t, c, k, axis=axis)
+
+    # set up the LHS: the collocation matrix + derivatives at boundaries
+    kl = ku = k
+    ab = np.zeros((2*kl + ku + 1, nt), dtype=np.float64, order='F')
+    _bspl._colloc(x, t, k, ab, offset=nleft)
+    if nleft > 0:
+        _bspl._handle_lhs_derivatives(t, k, x[0], ab, kl, ku,
+                                      deriv_l_ords.astype(np.dtype("long")))
+    if nright > 0:
+        _bspl._handle_lhs_derivatives(t, k, x[-1], ab, kl, ku,
+                                      deriv_r_ords.astype(np.dtype("long")),
+                                      offset=nt-nright)
+
+    # set up the RHS: values to interpolate (+ derivative values, if any)
+    extradim = prod(y.shape[1:])
+    rhs = np.empty((nt, extradim), dtype=y.dtype)
+    if nleft > 0:
+        rhs[:nleft] = deriv_l_vals.reshape(-1, extradim)
+    rhs[nleft:nt - nright] = y.reshape(-1, extradim)
+    if nright > 0:
+        rhs[nt - nright:] = deriv_r_vals.reshape(-1, extradim)
+
+    # solve Ab @ x = rhs; this is the relevant part of linalg.solve_banded
+    if check_finite:
+        ab, rhs = map(np.asarray_chkfinite, (ab, rhs))
+    gbsv, = get_lapack_funcs(('gbsv',), (ab, rhs))
+    lu, piv, c, info = gbsv(kl, ku, ab, rhs,
+                            overwrite_ab=True, overwrite_b=True)
+
+    if info > 0:
+        raise LinAlgError("Collocation matrix is singular.")
+    elif info < 0:
+        raise ValueError('illegal value in %d-th argument of internal gbsv' % -info)
+
+    c = np.ascontiguousarray(c.reshape((nt,) + y.shape[1:]))
+    return BSpline.construct_fast(t, c, k, axis=axis)
+
+
+def make_lsq_spline(x, y, t, k=3, w=None, axis=0, check_finite=True):
+    r"""Compute the (coefficients of) an LSQ (Least SQuared) based
+    fitting B-spline.
+
+    The result is a linear combination
+
+    .. math::
+
+            S(x) = \sum_j c_j B_j(x; t)
+
+    of the B-spline basis elements, :math:`B_j(x; t)`, which minimizes
+
+    .. math::
+
+        \sum_{j} \left( w_j \times (S(x_j) - y_j) \right)^2
+
+    Parameters
+    ----------
+    x : array_like, shape (m,)
+        Abscissas.
+    y : array_like, shape (m, ...)
+        Ordinates.
+    t : array_like, shape (n + k + 1,).
+        Knots.
+        Knots and data points must satisfy Schoenberg-Whitney conditions.
+    k : int, optional
+        B-spline degree. Default is cubic, ``k = 3``.
+    w : array_like, shape (m,), optional
+        Weights for spline fitting. Must be positive. If ``None``,
+        then weights are all equal.
+        Default is ``None``.
+    axis : int, optional
+        Interpolation axis. Default is zero.
+    check_finite : bool, optional
+        Whether to check that the input arrays contain only finite numbers.
+        Disabling may give a performance gain, but may result in problems
+        (crashes, non-termination) if the inputs do contain infinities or NaNs.
+        Default is True.
+
+    Returns
+    -------
+    b : a BSpline object of the degree ``k`` with knots ``t``.
+
+    See Also
+    --------
+    BSpline : base class representing the B-spline objects
+    make_interp_spline : a similar factory function for interpolating splines
+    LSQUnivariateSpline : a FITPACK-based spline fitting routine
+    splrep : a FITPACK-based fitting routine
+
+    Notes
+    -----
+    The number of data points must be larger than the spline degree ``k``.
+
+    Knots ``t`` must satisfy the Schoenberg-Whitney conditions,
+    i.e., there must be a subset of data points ``x[j]`` such that
+    ``t[j] < x[j] < t[j+k+1]``, for ``j=0, 1,...,n-k-2``.
+
+    Examples
+    --------
+    Generate some noisy data:
+
+    >>> import numpy as np
+    >>> import matplotlib.pyplot as plt
+    >>> rng = np.random.default_rng()
+    >>> x = np.linspace(-3, 3, 50)
+    >>> y = np.exp(-x**2) + 0.1 * rng.standard_normal(50)
+
+    Now fit a smoothing cubic spline with a pre-defined internal knots.
+    Here we make the knot vector (k+1)-regular by adding boundary knots:
+
+    >>> from scipy.interpolate import make_lsq_spline, BSpline
+    >>> t = [-1, 0, 1]
+    >>> k = 3
+    >>> t = np.r_[(x[0],)*(k+1),
+    ...           t,
+    ...           (x[-1],)*(k+1)]
+    >>> spl = make_lsq_spline(x, y, t, k)
+
+    For comparison, we also construct an interpolating spline for the same
+    set of data:
+
+    >>> from scipy.interpolate import make_interp_spline
+    >>> spl_i = make_interp_spline(x, y)
+
+    Plot both:
+
+    >>> xs = np.linspace(-3, 3, 100)
+    >>> plt.plot(x, y, 'ro', ms=5)
+    >>> plt.plot(xs, spl(xs), 'g-', lw=3, label='LSQ spline')
+    >>> plt.plot(xs, spl_i(xs), 'b-', lw=3, alpha=0.7, label='interp spline')
+    >>> plt.legend(loc='best')
+    >>> plt.show()
+
+    **NaN handling**: If the input arrays contain ``nan`` values, the result is
+    not useful since the underlying spline fitting routines cannot deal with
+    ``nan``. A workaround is to use zero weights for not-a-number data points:
+
+    >>> y[8] = np.nan
+    >>> w = np.isnan(y)
+    >>> y[w] = 0.
+    >>> tck = make_lsq_spline(x, y, t, w=~w)
+
+    Notice the need to replace a ``nan`` by a numerical value (precise value
+    does not matter as long as the corresponding weight is zero.)
+
+    """
+    x = _as_float_array(x, check_finite)
+    y = _as_float_array(y, check_finite)
+    t = _as_float_array(t, check_finite)
+    if w is not None:
+        w = _as_float_array(w, check_finite)
+    else:
+        w = np.ones_like(x)
+    k = operator.index(k)
+
+    axis = normalize_axis_index(axis, y.ndim)
+
+    y = np.moveaxis(y, axis, 0)    # now internally interp axis is zero
+
+    if x.ndim != 1 or np.any(x[1:] - x[:-1] <= 0):
+        raise ValueError("Expect x to be a 1-D sorted array_like.")
+    if x.shape[0] < k+1:
+        raise ValueError("Need more x points.")
+    if k < 0:
+        raise ValueError("Expect non-negative k.")
+    if t.ndim != 1 or np.any(t[1:] - t[:-1] < 0):
+        raise ValueError("Expect t to be a 1-D sorted array_like.")
+    if x.size != y.shape[0]:
+        raise ValueError(f'Shapes of x {x.shape} and y {y.shape} are incompatible')
+    if k > 0 and np.any((x < t[k]) | (x > t[-k])):
+        raise ValueError('Out of bounds w/ x = %s.' % x)
+    if x.size != w.size:
+        raise ValueError(f'Shapes of x {x.shape} and w {w.shape} are incompatible')
+
+    # number of coefficients
+    n = t.size - k - 1
+
+    # construct A.T @ A and rhs with A the collocation matrix, and
+    # rhs = A.T @ y for solving the LSQ problem  ``A.T @ A @ c = A.T @ y``
+    lower = True
+    extradim = prod(y.shape[1:])
+    ab = np.zeros((k+1, n), dtype=np.float64, order='F')
+    rhs = np.zeros((n, extradim), dtype=y.dtype, order='F')
+    _bspl._norm_eq_lsq(x, t, k,
+                       y.reshape(-1, extradim),
+                       w,
+                       ab, rhs)
+    rhs = rhs.reshape((n,) + y.shape[1:])
+
+    # have observation matrix & rhs, can solve the LSQ problem
+    cho_decomp = cholesky_banded(ab, overwrite_ab=True, lower=lower,
+                                 check_finite=check_finite)
+    c = cho_solve_banded((cho_decomp, lower), rhs, overwrite_b=True,
+                         check_finite=check_finite)
+
+    c = np.ascontiguousarray(c)
+    return BSpline.construct_fast(t, c, k, axis=axis)
+
+
+#############################
+#  Smoothing spline helpers #
+#############################
+
+def _compute_optimal_gcv_parameter(X, wE, y, w):
+    """
+    Returns an optimal regularization parameter from the GCV criteria [1].
+
+    Parameters
+    ----------
+    X : array, shape (5, n)
+        5 bands of the design matrix ``X`` stored in LAPACK banded storage.
+    wE : array, shape (5, n)
+        5 bands of the penalty matrix :math:`W^{-1} E` stored in LAPACK banded
+        storage.
+    y : array, shape (n,)
+        Ordinates.
+    w : array, shape (n,)
+        Vector of weights.
+
+    Returns
+    -------
+    lam : float
+        An optimal from the GCV criteria point of view regularization
+        parameter.
+
+    Notes
+    -----
+    No checks are performed.
+
+    References
+    ----------
+    .. [1] G. Wahba, "Estimating the smoothing parameter" in Spline models
+        for observational data, Philadelphia, Pennsylvania: Society for
+        Industrial and Applied Mathematics, 1990, pp. 45-65.
+        :doi:`10.1137/1.9781611970128`
+
+    """
+
+    def compute_banded_symmetric_XT_W_Y(X, w, Y):
+        """
+        Assuming that the product :math:`X^T W Y` is symmetric and both ``X``
+        and ``Y`` are 5-banded, compute the unique bands of the product.
+
+        Parameters
+        ----------
+        X : array, shape (5, n)
+            5 bands of the matrix ``X`` stored in LAPACK banded storage.
+        w : array, shape (n,)
+            Array of weights
+        Y : array, shape (5, n)
+            5 bands of the matrix ``Y`` stored in LAPACK banded storage.
+
+        Returns
+        -------
+        res : array, shape (4, n)
+            The result of the product :math:`X^T Y` stored in the banded way.
+
+        Notes
+        -----
+        As far as the matrices ``X`` and ``Y`` are 5-banded, their product
+        :math:`X^T W Y` is 7-banded. It is also symmetric, so we can store only
+        unique diagonals.
+
+        """
+        # compute W Y
+        W_Y = np.copy(Y)
+
+        W_Y[2] *= w
+        for i in range(2):
+            W_Y[i, 2 - i:] *= w[:-2 + i]
+            W_Y[3 + i, :-1 - i] *= w[1 + i:]
+
+        n = X.shape[1]
+        res = np.zeros((4, n))
+        for i in range(n):
+            for j in range(min(n-i, 4)):
+                res[-j-1, i + j] = sum(X[j:, i] * W_Y[:5-j, i + j])
+        return res
+
+    def compute_b_inv(A):
+        """
+        Inverse 3 central bands of matrix :math:`A=U^T D^{-1} U` assuming that
+        ``U`` is a unit upper triangular banded matrix using an algorithm
+        proposed in [1].
+
+        Parameters
+        ----------
+        A : array, shape (4, n)
+            Matrix to inverse, stored in LAPACK banded storage.
+
+        Returns
+        -------
+        B : array, shape (4, n)
+            3 unique bands of the symmetric matrix that is an inverse to ``A``.
+            The first row is filled with zeros.
+
+        Notes
+        -----
+        The algorithm is based on the cholesky decomposition and, therefore,
+        in case matrix ``A`` is close to not positive defined, the function
+        raises LinalgError.
+
+        Both matrices ``A`` and ``B`` are stored in LAPACK banded storage.
+
+        References
+        ----------
+        .. [1] M. F. Hutchinson and F. R. de Hoog, "Smoothing noisy data with
+            spline functions," Numerische Mathematik, vol. 47, no. 1,
+            pp. 99-106, 1985.
+            :doi:`10.1007/BF01389878`
+
+        """
+
+        def find_b_inv_elem(i, j, U, D, B):
+            rng = min(3, n - i - 1)
+            rng_sum = 0.
+            if j == 0:
+                # use 2-nd formula from [1]
+                for k in range(1, rng + 1):
+                    rng_sum -= U[-k - 1, i + k] * B[-k - 1, i + k]
+                rng_sum += D[i]
+                B[-1, i] = rng_sum
+            else:
+                # use 1-st formula from [1]
+                for k in range(1, rng + 1):
+                    diag = abs(k - j)
+                    ind = i + min(k, j)
+                    rng_sum -= U[-k - 1, i + k] * B[-diag - 1, ind + diag]
+                B[-j - 1, i + j] = rng_sum
+
+        U = cholesky_banded(A)
+        for i in range(2, 5):
+            U[-i, i-1:] /= U[-1, :-i+1]
+        D = 1. / (U[-1])**2
+        U[-1] /= U[-1]
+
+        n = U.shape[1]
+
+        B = np.zeros(shape=(4, n))
+        for i in range(n - 1, -1, -1):
+            for j in range(min(3, n - i - 1), -1, -1):
+                find_b_inv_elem(i, j, U, D, B)
+        # the first row contains garbage and should be removed
+        B[0] = [0.] * n
+        return B
+
+    def _gcv(lam, X, XtWX, wE, XtE):
+        r"""
+        Computes the generalized cross-validation criteria [1].
+
+        Parameters
+        ----------
+        lam : float, (:math:`\lambda \geq 0`)
+            Regularization parameter.
+        X : array, shape (5, n)
+            Matrix is stored in LAPACK banded storage.
+        XtWX : array, shape (4, n)
+            Product :math:`X^T W X` stored in LAPACK banded storage.
+        wE : array, shape (5, n)
+            Matrix :math:`W^{-1} E` stored in LAPACK banded storage.
+        XtE : array, shape (4, n)
+            Product :math:`X^T E` stored in LAPACK banded storage.
+
+        Returns
+        -------
+        res : float
+            Value of the GCV criteria with the regularization parameter
+            :math:`\lambda`.
+
+        Notes
+        -----
+        Criteria is computed from the formula (1.3.2) [3]:
+
+        .. math:
+
+        GCV(\lambda) = \dfrac{1}{n} \sum\limits_{k = 1}^{n} \dfrac{ \left(
+        y_k - f_{\lambda}(x_k) \right)^2}{\left( 1 - \Tr{A}/n\right)^2}$.
+        The criteria is discussed in section 1.3 [3].
+
+        The numerator is computed using (2.2.4) [3] and the denominator is
+        computed using an algorithm from [2] (see in the ``compute_b_inv``
+        function).
+
+        References
+        ----------
+        .. [1] G. Wahba, "Estimating the smoothing parameter" in Spline models
+            for observational data, Philadelphia, Pennsylvania: Society for
+            Industrial and Applied Mathematics, 1990, pp. 45-65.
+            :doi:`10.1137/1.9781611970128`
+        .. [2] M. F. Hutchinson and F. R. de Hoog, "Smoothing noisy data with
+            spline functions," Numerische Mathematik, vol. 47, no. 1,
+            pp. 99-106, 1985.
+            :doi:`10.1007/BF01389878`
+        .. [3] E. Zemlyanoy, "Generalized cross-validation smoothing splines",
+            BSc thesis, 2022. Might be available (in Russian)
+            `here <https://www.hse.ru/ba/am/students/diplomas/620910604>`_
+
+        """
+        # Compute the numerator from (2.2.4) [3]
+        n = X.shape[1]
+        c = solve_banded((2, 2), X + lam * wE, y)
+        res = np.zeros(n)
+        # compute ``W^{-1} E c`` with respect to banded-storage of ``E``
+        tmp = wE * c
+        for i in range(n):
+            for j in range(max(0, i - n + 3), min(5, i + 3)):
+                res[i] += tmp[j, i + 2 - j]
+        numer = np.linalg.norm(lam * res)**2 / n
+
+        # compute the denominator
+        lhs = XtWX + lam * XtE
+        try:
+            b_banded = compute_b_inv(lhs)
+            # compute the trace of the product b_banded @ XtX
+            tr = b_banded * XtWX
+            tr[:-1] *= 2
+            # find the denominator
+            denom = (1 - sum(sum(tr)) / n)**2
+        except LinAlgError:
+            # cholesky decomposition cannot be performed
+            raise ValueError('Seems like the problem is ill-posed')
+
+        res = numer / denom
+
+        return res
+
+    n = X.shape[1]
+
+    XtWX = compute_banded_symmetric_XT_W_Y(X, w, X)
+    XtE = compute_banded_symmetric_XT_W_Y(X, w, wE)
+
+    def fun(lam):
+        return _gcv(lam, X, XtWX, wE, XtE)
+
+    gcv_est = minimize_scalar(fun, bounds=(0, n), method='Bounded')
+    if gcv_est.success:
+        return gcv_est.x
+    raise ValueError(f"Unable to find minimum of the GCV "
+                     f"function: {gcv_est.message}")
+
+
+def _coeff_of_divided_diff(x):
+    """
+    Returns the coefficients of the divided difference.
+
+    Parameters
+    ----------
+    x : array, shape (n,)
+        Array which is used for the computation of divided difference.
+
+    Returns
+    -------
+    res : array_like, shape (n,)
+        Coefficients of the divided difference.
+
+    Notes
+    -----
+    Vector ``x`` should have unique elements, otherwise an error division by
+    zero might be raised.
+
+    No checks are performed.
+
+    """
+    n = x.shape[0]
+    res = np.zeros(n)
+    for i in range(n):
+        pp = 1.
+        for k in range(n):
+            if k != i:
+                pp *= (x[i] - x[k])
+        res[i] = 1. / pp
+    return res
+
+
+def make_smoothing_spline(x, y, w=None, lam=None):
+    r"""
+    Compute the (coefficients of) smoothing cubic spline function using
+    ``lam`` to control the tradeoff between the amount of smoothness of the
+    curve and its proximity to the data. In case ``lam`` is None, using the
+    GCV criteria [1] to find it.
+
+    A smoothing spline is found as a solution to the regularized weighted
+    linear regression problem:
+
+    .. math::
+
+        \sum\limits_{i=1}^n w_i\lvert y_i - f(x_i) \rvert^2 +
+        \lambda\int\limits_{x_1}^{x_n} (f^{(2)}(u))^2 d u
+
+    where :math:`f` is a spline function, :math:`w` is a vector of weights and
+    :math:`\lambda` is a regularization parameter.
+
+    If ``lam`` is None, we use the GCV criteria to find an optimal
+    regularization parameter, otherwise we solve the regularized weighted
+    linear regression problem with given parameter. The parameter controls
+    the tradeoff in the following way: the larger the parameter becomes, the
+    smoother the function gets.
+
+    Parameters
+    ----------
+    x : array_like, shape (n,)
+        Abscissas. `n` must be at least 5.
+    y : array_like, shape (n,)
+        Ordinates. `n` must be at least 5.
+    w : array_like, shape (n,), optional
+        Vector of weights. Default is ``np.ones_like(x)``.
+    lam : float, (:math:`\lambda \geq 0`), optional
+        Regularization parameter. If ``lam`` is None, then it is found from
+        the GCV criteria. Default is None.
+
+    Returns
+    -------
+    func : a BSpline object.
+        A callable representing a spline in the B-spline basis
+        as a solution of the problem of smoothing splines using
+        the GCV criteria [1] in case ``lam`` is None, otherwise using the
+        given parameter ``lam``.
+
+    Notes
+    -----
+    This algorithm is a clean room reimplementation of the algorithm
+    introduced by Woltring in FORTRAN [2]. The original version cannot be used
+    in SciPy source code because of the license issues. The details of the
+    reimplementation are discussed here (available only in Russian) [4].
+
+    If the vector of weights ``w`` is None, we assume that all the points are
+    equal in terms of weights, and vector of weights is vector of ones.
+
+    Note that in weighted residual sum of squares, weights are not squared:
+    :math:`\sum\limits_{i=1}^n w_i\lvert y_i - f(x_i) \rvert^2` while in
+    ``splrep`` the sum is built from the squared weights.
+
+    In cases when the initial problem is ill-posed (for example, the product
+    :math:`X^T W X` where :math:`X` is a design matrix is not a positive
+    defined matrix) a ValueError is raised.
+
+    References
+    ----------
+    .. [1] G. Wahba, "Estimating the smoothing parameter" in Spline models for
+        observational data, Philadelphia, Pennsylvania: Society for Industrial
+        and Applied Mathematics, 1990, pp. 45-65.
+        :doi:`10.1137/1.9781611970128`
+    .. [2] H. J. Woltring, A Fortran package for generalized, cross-validatory
+        spline smoothing and differentiation, Advances in Engineering
+        Software, vol. 8, no. 2, pp. 104-113, 1986.
+        :doi:`10.1016/0141-1195(86)90098-7`
+    .. [3] T. Hastie, J. Friedman, and R. Tisbshirani, "Smoothing Splines" in
+        The elements of Statistical Learning: Data Mining, Inference, and
+        prediction, New York: Springer, 2017, pp. 241-249.
+        :doi:`10.1007/978-0-387-84858-7`
+    .. [4] E. Zemlyanoy, "Generalized cross-validation smoothing splines",
+        BSc thesis, 2022.
+        `<https://www.hse.ru/ba/am/students/diplomas/620910604>`_ (in
+        Russian)
+
+    Examples
+    --------
+    Generate some noisy data
+
+    >>> import numpy as np
+    >>> np.random.seed(1234)
+    >>> n = 200
+    >>> def func(x):
+    ...    return x**3 + x**2 * np.sin(4 * x)
+    >>> x = np.sort(np.random.random_sample(n) * 4 - 2)
+    >>> y = func(x) + np.random.normal(scale=1.5, size=n)
+
+    Make a smoothing spline function
+
+    >>> from scipy.interpolate import make_smoothing_spline
+    >>> spl = make_smoothing_spline(x, y)
+
+    Plot both
+
+    >>> import matplotlib.pyplot as plt
+    >>> grid = np.linspace(x[0], x[-1], 400)
+    >>> plt.plot(grid, spl(grid), label='Spline')
+    >>> plt.plot(grid, func(grid), label='Original function')
+    >>> plt.scatter(x, y, marker='.')
+    >>> plt.legend(loc='best')
+    >>> plt.show()
+
+    """
+
+    x = np.ascontiguousarray(x, dtype=float)
+    y = np.ascontiguousarray(y, dtype=float)
+
+    if any(x[1:] - x[:-1] <= 0):
+        raise ValueError('``x`` should be an ascending array')
+
+    if x.ndim != 1 or y.ndim != 1 or x.shape[0] != y.shape[0]:
+        raise ValueError('``x`` and ``y`` should be one dimensional and the'
+                         ' same size')
+
+    if w is None:
+        w = np.ones(len(x))
+    else:
+        w = np.ascontiguousarray(w)
+        if any(w <= 0):
+            raise ValueError('Invalid vector of weights')
+
+    t = np.r_[[x[0]] * 3, x, [x[-1]] * 3]
+    n = x.shape[0]
+
+    if n <= 4:
+        raise ValueError('``x`` and ``y`` length must be at least 5')
+
+    # It is known that the solution to the stated minimization problem exists
+    # and is a natural cubic spline with vector of knots equal to the unique
+    # elements of ``x`` [3], so we will solve the problem in the basis of
+    # natural splines.
+
+    # create design matrix in the B-spline basis
+    X_bspl = BSpline.design_matrix(x, t, 3)
+    # move from B-spline basis to the basis of natural splines using equations
+    # (2.1.7) [4]
+    # central elements
+    X = np.zeros((5, n))
+    for i in range(1, 4):
+        X[i, 2: -2] = X_bspl[i: i - 4, 3: -3][np.diag_indices(n - 4)]
+
+    # first elements
+    X[1, 1] = X_bspl[0, 0]
+    X[2, :2] = ((x[2] + x[1] - 2 * x[0]) * X_bspl[0, 0],
+                X_bspl[1, 1] + X_bspl[1, 2])
+    X[3, :2] = ((x[2] - x[0]) * X_bspl[1, 1], X_bspl[2, 2])
+
+    # last elements
+    X[1, -2:] = (X_bspl[-3, -3], (x[-1] - x[-3]) * X_bspl[-2, -2])
+    X[2, -2:] = (X_bspl[-2, -3] + X_bspl[-2, -2],
+                 (2 * x[-1] - x[-2] - x[-3]) * X_bspl[-1, -1])
+    X[3, -2] = X_bspl[-1, -1]
+
+    # create penalty matrix and divide it by vector of weights: W^{-1} E
+    wE = np.zeros((5, n))
+    wE[2:, 0] = _coeff_of_divided_diff(x[:3]) / w[:3]
+    wE[1:, 1] = _coeff_of_divided_diff(x[:4]) / w[:4]
+    for j in range(2, n - 2):
+        wE[:, j] = (x[j+2] - x[j-2]) * _coeff_of_divided_diff(x[j-2:j+3])\
+                   / w[j-2: j+3]
+
+    wE[:-1, -2] = -_coeff_of_divided_diff(x[-4:]) / w[-4:]
+    wE[:-2, -1] = _coeff_of_divided_diff(x[-3:]) / w[-3:]
+    wE *= 6
+
+    if lam is None:
+        lam = _compute_optimal_gcv_parameter(X, wE, y, w)
+    elif lam < 0.:
+        raise ValueError('Regularization parameter should be non-negative')
+
+    # solve the initial problem in the basis of natural splines
+    c = solve_banded((2, 2), X + lam * wE, y)
+    # move back to B-spline basis using equations (2.2.10) [4]
+    c_ = np.r_[c[0] * (t[5] + t[4] - 2 * t[3]) + c[1],
+               c[0] * (t[5] - t[3]) + c[1],
+               c[1: -1],
+               c[-1] * (t[-4] - t[-6]) + c[-2],
+               c[-1] * (2 * t[-4] - t[-5] - t[-6]) + c[-2]]
+
+    return BSpline.construct_fast(t, c_, 3)
+
+
+########################
+#  FITPACK look-alikes #
+########################
+
+def fpcheck(x, t, k):
+    """ Check consistency of the data vector `x` and the knot vector `t`.
+
+    Return None if inputs are consistent, raises a ValueError otherwise.
+    """
+    # This routine is a clone of the `fpchec` Fortran routine, 
+    # https://github.com/scipy/scipy/blob/main/scipy/interpolate/fitpack/fpchec.f
+    # which carries the following comment:
+    #
+    # subroutine fpchec verifies the number and the position of the knots
+    #  t(j),j=1,2,...,n of a spline of degree k, in relation to the number
+    #  and the position of the data points x(i),i=1,2,...,m. if all of the
+    #  following conditions are fulfilled, the error parameter ier is set
+    #  to zero. if one of the conditions is violated ier is set to ten.
+    #      1) k+1 <= n-k-1 <= m
+    #      2) t(1) <= t(2) <= ... <= t(k+1)
+    #         t(n-k) <= t(n-k+1) <= ... <= t(n)
+    #      3) t(k+1) < t(k+2) < ... < t(n-k)
+    #      4) t(k+1) <= x(i) <= t(n-k)
+    #      5) the conditions specified by schoenberg and whitney must hold
+    #         for at least one subset of data points, i.e. there must be a
+    #         subset of data points y(j) such that
+    #             t(j) < y(j) < t(j+k+1), j=1,2,...,n-k-1
+    x = np.asarray(x)
+    t = np.asarray(t)
+
+    if x.ndim != 1 or t.ndim != 1:
+        raise ValueError(f"Expect `x` and `t` be 1D sequences. Got {x = } and {t = }")
+
+    m = x.shape[0]
+    n = t.shape[0]
+    nk1 = n - k - 1
+
+    # check condition no 1
+    # c      1) k+1 <= n-k-1 <= m
+    if not (k + 1 <= nk1 <= m):
+        raise ValueError(f"Need k+1 <= n-k-1 <= m. Got {m = }, {n = } and {k = }.")
+
+    # check condition no 2
+    # c      2) t(1) <= t(2) <= ... <= t(k+1)
+    # c         t(n-k) <= t(n-k+1) <= ... <= t(n)
+    if (t[:k+1] > t[1:k+2]).any():
+        raise ValueError(f"First k knots must be ordered; got {t = }.")
+
+    if (t[nk1:] < t[nk1-1:-1]).any():
+        raise ValueError(f"Last k knots must be ordered; got {t = }.")
+
+    # c  check condition no 3
+    # c      3) t(k+1) < t(k+2) < ... < t(n-k)
+    if (t[k+1:n-k] <= t[k:n-k-1]).any():
+        raise ValueError(f"Internal knots must be distinct. Got {t = }.")
+
+    # c  check condition no 4
+    # c      4) t(k+1) <= x(i) <= t(n-k)
+    # NB: FITPACK's fpchec only checks x[0] & x[-1], so we follow.
+    if (x[0] < t[k]) or (x[-1] > t[n-k-1]):
+        raise ValueError(f"Out of bounds: {x = } and {t = }.")
+
+    # c  check condition no 5
+    # c      5) the conditions specified by schoenberg and whitney must hold
+    # c         for at least one subset of data points, i.e. there must be a
+    # c         subset of data points y(j) such that
+    # c             t(j) < y(j) < t(j+k+1), j=1,2,...,n-k-1
+    mesg = f"Schoenberg-Whitney condition is violated with {t = } and {x =}."
+
+    if (x[0] >= t[k+1]) or (x[-1] <= t[n-k-2]):
+        raise ValueError(mesg)
+
+    m = x.shape[0]
+    l = k+1
+    nk3 = n - k - 3
+    if nk3 < 2:
+        return
+    for j in range(1, nk3+1):
+        tj = t[j]
+        l += 1
+        tl = t[l]
+        i = np.argmax(x > tj)
+        if i >= m-1:
+            raise ValueError(mesg)
+        if x[i] >= tl:
+            raise ValueError(mesg)
+    return

venv/lib/python3.10/site-packages/scipy/interpolate/_cubic.py

@@ -0,0 +1,970 @@
+"""Interpolation algorithms using piecewise cubic polynomials."""
+
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
+import warnings
+
+import numpy as np
+
+from scipy.linalg import solve, solve_banded
+
+from . import PPoly
+from ._polyint import _isscalar
+
+if TYPE_CHECKING:
+    from typing import Literal
+
+__all__ = ["CubicHermiteSpline", "PchipInterpolator", "pchip_interpolate",
+           "Akima1DInterpolator", "CubicSpline"]
+
+
+def prepare_input(x, y, axis, dydx=None):
+    """Prepare input for cubic spline interpolators.
+
+    All data are converted to numpy arrays and checked for correctness.
+    Axes equal to `axis` of arrays `y` and `dydx` are moved to be the 0th
+    axis. The value of `axis` is converted to lie in
+    [0, number of dimensions of `y`).
+    """
+
+    x, y = map(np.asarray, (x, y))
+    if np.issubdtype(x.dtype, np.complexfloating):
+        raise ValueError("`x` must contain real values.")
+    x = x.astype(float)
+
+    if np.issubdtype(y.dtype, np.complexfloating):
+        dtype = complex
+    else:
+        dtype = float
+
+    if dydx is not None:
+        dydx = np.asarray(dydx)
+        if y.shape != dydx.shape:
+            raise ValueError("The shapes of `y` and `dydx` must be identical.")
+        if np.issubdtype(dydx.dtype, np.complexfloating):
+            dtype = complex
+        dydx = dydx.astype(dtype, copy=False)
+
+    y = y.astype(dtype, copy=False)
+    axis = axis % y.ndim
+    if x.ndim != 1:
+        raise ValueError("`x` must be 1-dimensional.")
+    if x.shape[0] < 2:
+        raise ValueError("`x` must contain at least 2 elements.")
+    if x.shape[0] != y.shape[axis]:
+        raise ValueError(f"The length of `y` along `axis`={axis} doesn't "
+                         "match the length of `x`")
+
+    if not np.all(np.isfinite(x)):
+        raise ValueError("`x` must contain only finite values.")
+    if not np.all(np.isfinite(y)):
+        raise ValueError("`y` must contain only finite values.")
+
+    if dydx is not None and not np.all(np.isfinite(dydx)):
+        raise ValueError("`dydx` must contain only finite values.")
+
+    dx = np.diff(x)
+    if np.any(dx <= 0):
+        raise ValueError("`x` must be strictly increasing sequence.")
+
+    y = np.moveaxis(y, axis, 0)
+    if dydx is not None:
+        dydx = np.moveaxis(dydx, axis, 0)
+
+    return x, dx, y, axis, dydx
+
+
+class CubicHermiteSpline(PPoly):
+    """Piecewise-cubic interpolator matching values and first derivatives.
+
+    The result is represented as a `PPoly` instance.
+
+    Parameters
+    ----------
+    x : array_like, shape (n,)
+        1-D array containing values of the independent variable.
+        Values must be real, finite and in strictly increasing order.
+    y : array_like
+        Array containing values of the dependent variable. It can have
+        arbitrary number of dimensions, but the length along ``axis``
+        (see below) must match the length of ``x``. Values must be finite.
+    dydx : array_like
+        Array containing derivatives of the dependent variable. It can have
+        arbitrary number of dimensions, but the length along ``axis``
+        (see below) must match the length of ``x``. Values must be finite.
+    axis : int, optional
+        Axis along which `y` is assumed to be varying. Meaning that for
+        ``x[i]`` the corresponding values are ``np.take(y, i, axis=axis)``.
+        Default is 0.
+    extrapolate : {bool, 'periodic', None}, optional
+        If bool, determines whether to extrapolate to out-of-bounds points
+        based on first and last intervals, or to return NaNs. If 'periodic',
+        periodic extrapolation is used. If None (default), it is set to True.
+
+    Attributes
+    ----------
+    x : ndarray, shape (n,)
+        Breakpoints. The same ``x`` which was passed to the constructor.
+    c : ndarray, shape (4, n-1, ...)
+        Coefficients of the polynomials on each segment. The trailing
+        dimensions match the dimensions of `y`, excluding ``axis``.
+        For example, if `y` is 1-D, then ``c[k, i]`` is a coefficient for
+        ``(x-x[i])**(3-k)`` on the segment between ``x[i]`` and ``x[i+1]``.
+    axis : int
+        Interpolation axis. The same axis which was passed to the
+        constructor.
+
+    Methods
+    -------
+    __call__
+    derivative
+    antiderivative
+    integrate
+    roots
+
+    See Also
+    --------
+    Akima1DInterpolator : Akima 1D interpolator.
+    PchipInterpolator : PCHIP 1-D monotonic cubic interpolator.
+    CubicSpline : Cubic spline data interpolator.
+    PPoly : Piecewise polynomial in terms of coefficients and breakpoints
+
+    Notes
+    -----
+    If you want to create a higher-order spline matching higher-order
+    derivatives, use `BPoly.from_derivatives`.
+
+    References
+    ----------
+    .. [1] `Cubic Hermite spline
+            <https://en.wikipedia.org/wiki/Cubic_Hermite_spline>`_
+            on Wikipedia.
+    """
+
+    def __init__(self, x, y, dydx, axis=0, extrapolate=None):
+        if extrapolate is None:
+            extrapolate = True
+
+        x, dx, y, axis, dydx = prepare_input(x, y, axis, dydx)
+
+        dxr = dx.reshape([dx.shape[0]] + [1] * (y.ndim - 1))
+        slope = np.diff(y, axis=0) / dxr
+        t = (dydx[:-1] + dydx[1:] - 2 * slope) / dxr
+
+        c = np.empty((4, len(x) - 1) + y.shape[1:], dtype=t.dtype)
+        c[0] = t / dxr
+        c[1] = (slope - dydx[:-1]) / dxr - t
+        c[2] = dydx[:-1]
+        c[3] = y[:-1]
+
+        super().__init__(c, x, extrapolate=extrapolate)
+        self.axis = axis
+
+
+class PchipInterpolator(CubicHermiteSpline):
+    r"""PCHIP 1-D monotonic cubic interpolation.
+
+    ``x`` and ``y`` are arrays of values used to approximate some function f,
+    with ``y = f(x)``. The interpolant uses monotonic cubic splines
+    to find the value of new points. (PCHIP stands for Piecewise Cubic
+    Hermite Interpolating Polynomial).
+
+    Parameters
+    ----------
+    x : ndarray, shape (npoints, )
+        A 1-D array of monotonically increasing real values. ``x`` cannot
+        include duplicate values (otherwise f is overspecified)
+    y : ndarray, shape (..., npoints, ...)
+        A N-D array of real values. ``y``'s length along the interpolation
+        axis must be equal to the length of ``x``. Use the ``axis``
+        parameter to select the interpolation axis.
+
+        .. deprecated:: 1.13.0
+            Complex data is deprecated and will raise an error in SciPy 1.15.0.
+            If you are trying to use the real components of the passed array,
+            use ``np.real`` on ``y``.
+
+    axis : int, optional
+        Axis in the ``y`` array corresponding to the x-coordinate values. Defaults
+        to ``axis=0``.
+    extrapolate : bool, optional
+        Whether to extrapolate to out-of-bounds points based on first
+        and last intervals, or to return NaNs.
+
+    Methods
+    -------
+    __call__
+    derivative
+    antiderivative
+    roots
+
+    See Also
+    --------
+    CubicHermiteSpline : Piecewise-cubic interpolator.
+    Akima1DInterpolator : Akima 1D interpolator.
+    CubicSpline : Cubic spline data interpolator.
+    PPoly : Piecewise polynomial in terms of coefficients and breakpoints.
+
+    Notes
+    -----
+    The interpolator preserves monotonicity in the interpolation data and does
+    not overshoot if the data is not smooth.
+
+    The first derivatives are guaranteed to be continuous, but the second
+    derivatives may jump at :math:`x_k`.
+
+    Determines the derivatives at the points :math:`x_k`, :math:`f'_k`,
+    by using PCHIP algorithm [1]_.
+
+    Let :math:`h_k = x_{k+1} - x_k`, and  :math:`d_k = (y_{k+1} - y_k) / h_k`
+    are the slopes at internal points :math:`x_k`.
+    If the signs of :math:`d_k` and :math:`d_{k-1}` are different or either of
+    them equals zero, then :math:`f'_k = 0`. Otherwise, it is given by the
+    weighted harmonic mean
+
+    .. math::
+
+        \frac{w_1 + w_2}{f'_k} = \frac{w_1}{d_{k-1}} + \frac{w_2}{d_k}
+
+    where :math:`w_1 = 2 h_k + h_{k-1}` and :math:`w_2 = h_k + 2 h_{k-1}`.
+
+    The end slopes are set using a one-sided scheme [2]_.
+
+
+    References
+    ----------
+    .. [1] F. N. Fritsch and J. Butland,
+           A method for constructing local
+           monotone piecewise cubic interpolants,
+           SIAM J. Sci. Comput., 5(2), 300-304 (1984).
+           :doi:`10.1137/0905021`.
+    .. [2] see, e.g., C. Moler, Numerical Computing with Matlab, 2004.
+           :doi:`10.1137/1.9780898717952`
+
+    """
+
+    def __init__(self, x, y, axis=0, extrapolate=None):
+        x, _, y, axis, _ = prepare_input(x, y, axis)
+        if np.iscomplexobj(y):
+            msg = ("`PchipInterpolator` only works with real values for `y`. "
+                   "Passing an array with a complex dtype for `y` is deprecated "
+                   "and will raise an error in SciPy 1.15.0. If you are trying to "
+                   "use the real components of the passed array, use `np.real` on "
+                   "the array before passing to `PchipInterpolator`.")
+            warnings.warn(msg, DeprecationWarning, stacklevel=2)
+        xp = x.reshape((x.shape[0],) + (1,)*(y.ndim-1))
+        dk = self._find_derivatives(xp, y)
+        super().__init__(x, y, dk, axis=0, extrapolate=extrapolate)
+        self.axis = axis
+
+    @staticmethod
+    def _edge_case(h0, h1, m0, m1):
+        # one-sided three-point estimate for the derivative
+        d = ((2*h0 + h1)*m0 - h0*m1) / (h0 + h1)
+
+        # try to preserve shape
+        mask = np.sign(d) != np.sign(m0)
+        mask2 = (np.sign(m0) != np.sign(m1)) & (np.abs(d) > 3.*np.abs(m0))
+        mmm = (~mask) & mask2
+
+        d[mask] = 0.
+        d[mmm] = 3.*m0[mmm]
+
+        return d
+
+    @staticmethod
+    def _find_derivatives(x, y):
+        # Determine the derivatives at the points y_k, d_k, by using
+        #  PCHIP algorithm is:
+        # We choose the derivatives at the point x_k by
+        # Let m_k be the slope of the kth segment (between k and k+1)
+        # If m_k=0 or m_{k-1}=0 or sgn(m_k) != sgn(m_{k-1}) then d_k == 0
+        # else use weighted harmonic mean:
+        #   w_1 = 2h_k + h_{k-1}, w_2 = h_k + 2h_{k-1}
+        #   1/d_k = 1/(w_1 + w_2)*(w_1 / m_k + w_2 / m_{k-1})
+        #   where h_k is the spacing between x_k and x_{k+1}
+        y_shape = y.shape
+        if y.ndim == 1:
+            # So that _edge_case doesn't end up assigning to scalars
+            x = x[:, None]
+            y = y[:, None]
+
+        hk = x[1:] - x[:-1]
+        mk = (y[1:] - y[:-1]) / hk
+
+        if y.shape[0] == 2:
+            # edge case: only have two points, use linear interpolation
+            dk = np.zeros_like(y)
+            dk[0] = mk
+            dk[1] = mk
+            return dk.reshape(y_shape)
+
+        smk = np.sign(mk)
+        condition = (smk[1:] != smk[:-1]) | (mk[1:] == 0) | (mk[:-1] == 0)
+
+        w1 = 2*hk[1:] + hk[:-1]
+        w2 = hk[1:] + 2*hk[:-1]
+
+        # values where division by zero occurs will be excluded
+        # by 'condition' afterwards
+        with np.errstate(divide='ignore', invalid='ignore'):
+            whmean = (w1/mk[:-1] + w2/mk[1:]) / (w1 + w2)
+
+        dk = np.zeros_like(y)
+        dk[1:-1][condition] = 0.0
+        dk[1:-1][~condition] = 1.0 / whmean[~condition]
+
+        # special case endpoints, as suggested in
+        # Cleve Moler, Numerical Computing with MATLAB, Chap 3.6 (pchiptx.m)
+        dk[0] = PchipInterpolator._edge_case(hk[0], hk[1], mk[0], mk[1])
+        dk[-1] = PchipInterpolator._edge_case(hk[-1], hk[-2], mk[-1], mk[-2])
+
+        return dk.reshape(y_shape)
+
+
+def pchip_interpolate(xi, yi, x, der=0, axis=0):
+    """
+    Convenience function for pchip interpolation.
+
+    xi and yi are arrays of values used to approximate some function f,
+    with ``yi = f(xi)``. The interpolant uses monotonic cubic splines
+    to find the value of new points x and the derivatives there.
+
+    See `scipy.interpolate.PchipInterpolator` for details.
+
+    Parameters
+    ----------
+    xi : array_like
+        A sorted list of x-coordinates, of length N.
+    yi : array_like
+        A 1-D array of real values. `yi`'s length along the interpolation
+        axis must be equal to the length of `xi`. If N-D array, use axis
+        parameter to select correct axis.
+
+        .. deprecated:: 1.13.0
+            Complex data is deprecated and will raise an error in
+            SciPy 1.15.0. If you are trying to use the real components of
+            the passed array, use ``np.real`` on `yi`.
+
+    x : scalar or array_like
+        Of length M.
+    der : int or list, optional
+        Derivatives to extract. The 0th derivative can be included to
+        return the function value.
+    axis : int, optional
+        Axis in the yi array corresponding to the x-coordinate values.
+
+    Returns
+    -------
+    y : scalar or array_like
+        The result, of length R or length M or M by R.
+
+    See Also
+    --------
+    PchipInterpolator : PCHIP 1-D monotonic cubic interpolator.
+
+    Examples
+    --------
+    We can interpolate 2D observed data using pchip interpolation:
+
+    >>> import numpy as np
+    >>> import matplotlib.pyplot as plt
+    >>> from scipy.interpolate import pchip_interpolate
+    >>> x_observed = np.linspace(0.0, 10.0, 11)
+    >>> y_observed = np.sin(x_observed)
+    >>> x = np.linspace(min(x_observed), max(x_observed), num=100)
+    >>> y = pchip_interpolate(x_observed, y_observed, x)
+    >>> plt.plot(x_observed, y_observed, "o", label="observation")
+    >>> plt.plot(x, y, label="pchip interpolation")
+    >>> plt.legend()
+    >>> plt.show()
+
+    """
+    P = PchipInterpolator(xi, yi, axis=axis)
+
+    if der == 0:
+        return P(x)
+    elif _isscalar(der):
+        return P.derivative(der)(x)
+    else:
+        return [P.derivative(nu)(x) for nu in der]
+
+
+class Akima1DInterpolator(CubicHermiteSpline):
+    r"""
+    Akima interpolator
+
+    Fit piecewise cubic polynomials, given vectors x and y. The interpolation
+    method by Akima uses a continuously differentiable sub-spline built from
+    piecewise cubic polynomials. The resultant curve passes through the given
+    data points and will appear smooth and natural.
+
+    Parameters
+    ----------
+    x : ndarray, shape (npoints, )
+        1-D array of monotonically increasing real values.
+    y : ndarray, shape (..., npoints, ...)
+        N-D array of real values. The length of ``y`` along the interpolation axis
+        must be equal to the length of ``x``. Use the ``axis`` parameter to
+        select the interpolation axis.
+
+        .. deprecated:: 1.13.0
+            Complex data is deprecated and will raise an error in SciPy 1.15.0.
+            If you are trying to use the real components of the passed array,
+            use ``np.real`` on ``y``.
+
+    axis : int, optional
+        Axis in the ``y`` array corresponding to the x-coordinate values. Defaults
+        to ``axis=0``.
+    method : {'akima', 'makima'}, optional
+        If ``"makima"``, use the modified Akima interpolation [2]_.
+        Defaults to ``"akima"``, use the Akima interpolation [1]_.
+
+        .. versionadded:: 1.13.0
+
+    Methods
+    -------
+    __call__
+    derivative
+    antiderivative
+    roots
+
+    See Also
+    --------
+    PchipInterpolator : PCHIP 1-D monotonic cubic interpolator.
+    CubicSpline : Cubic spline data interpolator.
+    PPoly : Piecewise polynomial in terms of coefficients and breakpoints
+
+    Notes
+    -----
+    .. versionadded:: 0.14
+
+    Use only for precise data, as the fitted curve passes through the given
+    points exactly. This routine is useful for plotting a pleasingly smooth
+    curve through a few given points for purposes of plotting.
+
+    Let :math:`\delta_i = (y_{i+1} - y_i) / (x_{i+1} - x_i)` be the slopes of
+    the interval :math:`\left[x_i, x_{i+1}\right)`. Akima's derivative at
+    :math:`x_i` is defined as:
+
+    .. math::
+
+        d_i = \frac{w_1}{w_1 + w_2}\delta_{i-1} + \frac{w_2}{w_1 + w_2}\delta_i
+
+    In the Akima interpolation [1]_ (``method="akima"``), the weights are:
+
+    .. math::
+
+        \begin{aligned}
+        w_1 &= |\delta_{i+1} - \delta_i| \\
+        w_2 &= |\delta_{i-1} - \delta_{i-2}|
+        \end{aligned}
+
+    In the modified Akima interpolation [2]_ (``method="makima"``),
+    to eliminate overshoot and avoid edge cases of both numerator and
+    denominator being equal to 0, the weights are modified as follows:
+
+    .. math::
+
+        \begin{align*}
+        w_1 &= |\delta_{i+1} - \delta_i| + |\delta_{i+1} + \delta_i| / 2 \\
+        w_2 &= |\delta_{i-1} - \delta_{i-2}| + |\delta_{i-1} + \delta_{i-2}| / 2
+        \end{align*}
+
+    Examples
+    --------
+    Comparison of ``method="akima"`` and ``method="makima"``:
+
+    >>> import numpy as np
+    >>> from scipy.interpolate import Akima1DInterpolator
+    >>> import matplotlib.pyplot as plt
+    >>> x = np.linspace(1, 7, 7)
+    >>> y = np.array([-1, -1, -1, 0, 1, 1, 1])
+    >>> xs = np.linspace(min(x), max(x), num=100)
+    >>> y_akima = Akima1DInterpolator(x, y, method="akima")(xs)
+    >>> y_makima = Akima1DInterpolator(x, y, method="makima")(xs)
+
+    >>> fig, ax = plt.subplots()
+    >>> ax.plot(x, y, "o", label="data")
+    >>> ax.plot(xs, y_akima, label="akima")
+    >>> ax.plot(xs, y_makima, label="makima")
+    >>> ax.legend()
+    >>> fig.show()
+
+    The overshoot that occured in ``"akima"`` has been avoided in ``"makima"``.
+
+    References
+    ----------
+    .. [1] A new method of interpolation and smooth curve fitting based
+           on local procedures. Hiroshi Akima, J. ACM, October 1970, 17(4),
+           589-602. :doi:`10.1145/321607.321609`
+    .. [2] Makima Piecewise Cubic Interpolation. Cleve Moler and Cosmin Ionita, 2019.
+           https://blogs.mathworks.com/cleve/2019/04/29/makima-piecewise-cubic-interpolation/
+
+    """
+
+    def __init__(self, x, y, axis=0, *, method: Literal["akima", "makima"]="akima"):
+        if method not in {"akima", "makima"}:
+            raise NotImplementedError(f"`method`={method} is unsupported.")
+        # Original implementation in MATLAB by N. Shamsundar (BSD licensed), see
+        # https://www.mathworks.com/matlabcentral/fileexchange/1814-akima-interpolation
+        x, dx, y, axis, _ = prepare_input(x, y, axis)
+
+        if np.iscomplexobj(y):
+            msg = ("`Akima1DInterpolator` only works with real values for `y`. "
+                   "Passing an array with a complex dtype for `y` is deprecated "
+                   "and will raise an error in SciPy 1.15.0. If you are trying to "
+                   "use the real components of the passed array, use `np.real` on "
+                   "the array before passing to `Akima1DInterpolator`.")
+            warnings.warn(msg, DeprecationWarning, stacklevel=2)
+
+        # determine slopes between breakpoints
+        m = np.empty((x.size + 3, ) + y.shape[1:])
+        dx = dx[(slice(None), ) + (None, ) * (y.ndim - 1)]
+        m[2:-2] = np.diff(y, axis=0) / dx
+
+        # add two additional points on the left ...
+        m[1] = 2. * m[2] - m[3]
+        m[0] = 2. * m[1] - m[2]
+        # ... and on the right
+        m[-2] = 2. * m[-3] - m[-4]
+        m[-1] = 2. * m[-2] - m[-3]
+
+        # if m1 == m2 != m3 == m4, the slope at the breakpoint is not
+        # defined. This is the fill value:
+        t = .5 * (m[3:] + m[:-3])
+        # get the denominator of the slope t
+        dm = np.abs(np.diff(m, axis=0))
+        if method == "makima":
+            pm = np.abs(m[1:] + m[:-1])
+            f1 = dm[2:] + 0.5 * pm[2:]
+            f2 = dm[:-2] + 0.5 * pm[:-2]
+        else:
+            f1 = dm[2:]
+            f2 = dm[:-2]
+        f12 = f1 + f2
+        # These are the mask of where the slope at breakpoint is defined:
+        ind = np.nonzero(f12 > 1e-9 * np.max(f12, initial=-np.inf))
+        x_ind, y_ind = ind[0], ind[1:]
+        # Set the slope at breakpoint
+        t[ind] = (f1[ind] * m[(x_ind + 1,) + y_ind] +
+                  f2[ind] * m[(x_ind + 2,) + y_ind]) / f12[ind]
+
+        super().__init__(x, y, t, axis=0, extrapolate=False)
+        self.axis = axis
+
+    def extend(self, c, x, right=True):
+        raise NotImplementedError("Extending a 1-D Akima interpolator is not "
+                                  "yet implemented")
+
+    # These are inherited from PPoly, but they do not produce an Akima
+    # interpolator. Hence stub them out.
+    @classmethod
+    def from_spline(cls, tck, extrapolate=None):
+        raise NotImplementedError("This method does not make sense for "
+                                  "an Akima interpolator.")
+
+    @classmethod
+    def from_bernstein_basis(cls, bp, extrapolate=None):
+        raise NotImplementedError("This method does not make sense for "
+                                  "an Akima interpolator.")
+
+
+class CubicSpline(CubicHermiteSpline):
+    """Cubic spline data interpolator.
+
+    Interpolate data with a piecewise cubic polynomial which is twice
+    continuously differentiable [1]_. The result is represented as a `PPoly`
+    instance with breakpoints matching the given data.
+
+    Parameters
+    ----------
+    x : array_like, shape (n,)
+        1-D array containing values of the independent variable.
+        Values must be real, finite and in strictly increasing order.
+    y : array_like
+        Array containing values of the dependent variable. It can have
+        arbitrary number of dimensions, but the length along ``axis``
+        (see below) must match the length of ``x``. Values must be finite.
+    axis : int, optional
+        Axis along which `y` is assumed to be varying. Meaning that for
+        ``x[i]`` the corresponding values are ``np.take(y, i, axis=axis)``.
+        Default is 0.
+    bc_type : string or 2-tuple, optional
+        Boundary condition type. Two additional equations, given by the
+        boundary conditions, are required to determine all coefficients of
+        polynomials on each segment [2]_.
+
+        If `bc_type` is a string, then the specified condition will be applied
+        at both ends of a spline. Available conditions are:
+
+        * 'not-a-knot' (default): The first and second segment at a curve end
+          are the same polynomial. It is a good default when there is no
+          information on boundary conditions.
+        * 'periodic': The interpolated functions is assumed to be periodic
+          of period ``x[-1] - x[0]``. The first and last value of `y` must be
+          identical: ``y[0] == y[-1]``. This boundary condition will result in
+          ``y'[0] == y'[-1]`` and ``y''[0] == y''[-1]``.
+        * 'clamped': The first derivative at curves ends are zero. Assuming
+          a 1D `y`, ``bc_type=((1, 0.0), (1, 0.0))`` is the same condition.
+        * 'natural': The second derivative at curve ends are zero. Assuming
+          a 1D `y`, ``bc_type=((2, 0.0), (2, 0.0))`` is the same condition.
+
+        If `bc_type` is a 2-tuple, the first and the second value will be
+        applied at the curve start and end respectively. The tuple values can
+        be one of the previously mentioned strings (except 'periodic') or a
+        tuple `(order, deriv_values)` allowing to specify arbitrary
+        derivatives at curve ends:
+
+        * `order`: the derivative order, 1 or 2.
+        * `deriv_value`: array_like containing derivative values, shape must
+          be the same as `y`, excluding ``axis`` dimension. For example, if
+          `y` is 1-D, then `deriv_value` must be a scalar. If `y` is 3-D with
+          the shape (n0, n1, n2) and axis=2, then `deriv_value` must be 2-D
+          and have the shape (n0, n1).
+    extrapolate : {bool, 'periodic', None}, optional
+        If bool, determines whether to extrapolate to out-of-bounds points
+        based on first and last intervals, or to return NaNs. If 'periodic',
+        periodic extrapolation is used. If None (default), ``extrapolate`` is
+        set to 'periodic' for ``bc_type='periodic'`` and to True otherwise.
+
+    Attributes
+    ----------
+    x : ndarray, shape (n,)
+        Breakpoints. The same ``x`` which was passed to the constructor.
+    c : ndarray, shape (4, n-1, ...)
+        Coefficients of the polynomials on each segment. The trailing
+        dimensions match the dimensions of `y`, excluding ``axis``.
+        For example, if `y` is 1-d, then ``c[k, i]`` is a coefficient for
+        ``(x-x[i])**(3-k)`` on the segment between ``x[i]`` and ``x[i+1]``.
+    axis : int
+        Interpolation axis. The same axis which was passed to the
+        constructor.
+
+    Methods
+    -------
+    __call__
+    derivative
+    antiderivative
+    integrate
+    roots
+
+    See Also
+    --------
+    Akima1DInterpolator : Akima 1D interpolator.
+    PchipInterpolator : PCHIP 1-D monotonic cubic interpolator.
+    PPoly : Piecewise polynomial in terms of coefficients and breakpoints.
+
+    Notes
+    -----
+    Parameters `bc_type` and ``extrapolate`` work independently, i.e. the
+    former controls only construction of a spline, and the latter only
+    evaluation.
+
+    When a boundary condition is 'not-a-knot' and n = 2, it is replaced by
+    a condition that the first derivative is equal to the linear interpolant
+    slope. When both boundary conditions are 'not-a-knot' and n = 3, the
+    solution is sought as a parabola passing through given points.
+
+    When 'not-a-knot' boundary conditions is applied to both ends, the
+    resulting spline will be the same as returned by `splrep` (with ``s=0``)
+    and `InterpolatedUnivariateSpline`, but these two methods use a
+    representation in B-spline basis.
+
+    .. versionadded:: 0.18.0
+
+    Examples
+    --------
+    In this example the cubic spline is used to interpolate a sampled sinusoid.
+    You can see that the spline continuity property holds for the first and
+    second derivatives and violates only for the third derivative.
+
+    >>> import numpy as np
+    >>> from scipy.interpolate import CubicSpline
+    >>> import matplotlib.pyplot as plt
+    >>> x = np.arange(10)
+    >>> y = np.sin(x)
+    >>> cs = CubicSpline(x, y)
+    >>> xs = np.arange(-0.5, 9.6, 0.1)
+    >>> fig, ax = plt.subplots(figsize=(6.5, 4))
+    >>> ax.plot(x, y, 'o', label='data')
+    >>> ax.plot(xs, np.sin(xs), label='true')
+    >>> ax.plot(xs, cs(xs), label="S")
+    >>> ax.plot(xs, cs(xs, 1), label="S'")
+    >>> ax.plot(xs, cs(xs, 2), label="S''")
+    >>> ax.plot(xs, cs(xs, 3), label="S'''")
+    >>> ax.set_xlim(-0.5, 9.5)
+    >>> ax.legend(loc='lower left', ncol=2)
+    >>> plt.show()
+
+    In the second example, the unit circle is interpolated with a spline. A
+    periodic boundary condition is used. You can see that the first derivative
+    values, ds/dx=0, ds/dy=1 at the periodic point (1, 0) are correctly
+    computed. Note that a circle cannot be exactly represented by a cubic
+    spline. To increase precision, more breakpoints would be required.
+
+    >>> theta = 2 * np.pi * np.linspace(0, 1, 5)
+    >>> y = np.c_[np.cos(theta), np.sin(theta)]
+    >>> cs = CubicSpline(theta, y, bc_type='periodic')
+    >>> print("ds/dx={:.1f} ds/dy={:.1f}".format(cs(0, 1)[0], cs(0, 1)[1]))
+    ds/dx=0.0 ds/dy=1.0
+    >>> xs = 2 * np.pi * np.linspace(0, 1, 100)
+    >>> fig, ax = plt.subplots(figsize=(6.5, 4))
+    >>> ax.plot(y[:, 0], y[:, 1], 'o', label='data')
+    >>> ax.plot(np.cos(xs), np.sin(xs), label='true')
+    >>> ax.plot(cs(xs)[:, 0], cs(xs)[:, 1], label='spline')
+    >>> ax.axes.set_aspect('equal')
+    >>> ax.legend(loc='center')
+    >>> plt.show()
+
+    The third example is the interpolation of a polynomial y = x**3 on the
+    interval 0 <= x<= 1. A cubic spline can represent this function exactly.
+    To achieve that we need to specify values and first derivatives at
+    endpoints of the interval. Note that y' = 3 * x**2 and thus y'(0) = 0 and
+    y'(1) = 3.
+
+    >>> cs = CubicSpline([0, 1], [0, 1], bc_type=((1, 0), (1, 3)))
+    >>> x = np.linspace(0, 1)
+    >>> np.allclose(x**3, cs(x))
+    True
+
+    References
+    ----------
+    .. [1] `Cubic Spline Interpolation
+            <https://en.wikiversity.org/wiki/Cubic_Spline_Interpolation>`_
+            on Wikiversity.
+    .. [2] Carl de Boor, "A Practical Guide to Splines", Springer-Verlag, 1978.
+    """
+
+    def __init__(self, x, y, axis=0, bc_type='not-a-knot', extrapolate=None):
+        x, dx, y, axis, _ = prepare_input(x, y, axis)
+        n = len(x)
+
+        bc, y = self._validate_bc(bc_type, y, y.shape[1:], axis)
+
+        if extrapolate is None:
+            if bc[0] == 'periodic':
+                extrapolate = 'periodic'
+            else:
+                extrapolate = True
+
+        if y.size == 0:
+            # bail out early for zero-sized arrays
+            s = np.zeros_like(y)
+        else:
+            dxr = dx.reshape([dx.shape[0]] + [1] * (y.ndim - 1))
+            slope = np.diff(y, axis=0) / dxr
+
+            # If bc is 'not-a-knot' this change is just a convention.
+            # If bc is 'periodic' then we already checked that y[0] == y[-1],
+            # and the spline is just a constant, we handle this case in the
+            # same way by setting the first derivatives to slope, which is 0.
+            if n == 2:
+                if bc[0] in ['not-a-knot', 'periodic']:
+                    bc[0] = (1, slope[0])
+                if bc[1] in ['not-a-knot', 'periodic']:
+                    bc[1] = (1, slope[0])
+
+            # This is a special case, when both conditions are 'not-a-knot'
+            # and n == 3. In this case 'not-a-knot' can't be handled regularly
+            # as the both conditions are identical. We handle this case by
+            # constructing a parabola passing through given points.
+            if n == 3 and bc[0] == 'not-a-knot' and bc[1] == 'not-a-knot':
+                A = np.zeros((3, 3))  # This is a standard matrix.
+                b = np.empty((3,) + y.shape[1:], dtype=y.dtype)
+
+                A[0, 0] = 1
+                A[0, 1] = 1
+                A[1, 0] = dx[1]
+                A[1, 1] = 2 * (dx[0] + dx[1])
+                A[1, 2] = dx[0]
+                A[2, 1] = 1
+                A[2, 2] = 1
+
+                b[0] = 2 * slope[0]
+                b[1] = 3 * (dxr[0] * slope[1] + dxr[1] * slope[0])
+                b[2] = 2 * slope[1]
+
+                s = solve(A, b, overwrite_a=True, overwrite_b=True,
+                          check_finite=False)
+            elif n == 3 and bc[0] == 'periodic':
+                # In case when number of points is 3 we compute the derivatives
+                # manually
+                t = (slope / dxr).sum(0) / (1. / dxr).sum(0)
+                s = np.broadcast_to(t, (n,) + y.shape[1:])
+            else:
+                # Find derivative values at each x[i] by solving a tridiagonal
+                # system.
+                A = np.zeros((3, n))  # This is a banded matrix representation.
+                b = np.empty((n,) + y.shape[1:], dtype=y.dtype)
+
+                # Filling the system for i=1..n-2
+                #                         (x[i-1] - x[i]) * s[i-1] +\
+                # 2 * ((x[i] - x[i-1]) + (x[i+1] - x[i])) * s[i]   +\
+                #                         (x[i] - x[i-1]) * s[i+1] =\
+                #       3 * ((x[i+1] - x[i])*(y[i] - y[i-1])/(x[i] - x[i-1]) +\
+                #           (x[i] - x[i-1])*(y[i+1] - y[i])/(x[i+1] - x[i]))
+
+                A[1, 1:-1] = 2 * (dx[:-1] + dx[1:])  # The diagonal
+                A[0, 2:] = dx[:-1]                   # The upper diagonal
+                A[-1, :-2] = dx[1:]                  # The lower diagonal
+
+                b[1:-1] = 3 * (dxr[1:] * slope[:-1] + dxr[:-1] * slope[1:])
+
+                bc_start, bc_end = bc
+
+                if bc_start == 'periodic':
+                    # Due to the periodicity, and because y[-1] = y[0], the
+                    # linear system has (n-1) unknowns/equations instead of n:
+                    A = A[:, 0:-1]
+                    A[1, 0] = 2 * (dx[-1] + dx[0])
+                    A[0, 1] = dx[-1]
+
+                    b = b[:-1]
+
+                    # Also, due to the periodicity, the system is not tri-diagonal.
+                    # We need to compute a "condensed" matrix of shape (n-2, n-2).
+                    # See https://web.archive.org/web/20151220180652/http://www.cfm.brown.edu/people/gk/chap6/node14.html
+                    # for more explanations.
+                    # The condensed matrix is obtained by removing the last column
+                    # and last row of the (n-1, n-1) system matrix. The removed
+                    # values are saved in scalar variables with the (n-1, n-1)
+                    # system matrix indices forming their names:
+                    a_m1_0 = dx[-2]  # lower left corner value: A[-1, 0]
+                    a_m1_m2 = dx[-1]
+                    a_m1_m1 = 2 * (dx[-1] + dx[-2])
+                    a_m2_m1 = dx[-3]
+                    a_0_m1 = dx[0]
+
+                    b[0] = 3 * (dxr[0] * slope[-1] + dxr[-1] * slope[0])
+                    b[-1] = 3 * (dxr[-1] * slope[-2] + dxr[-2] * slope[-1])
+
+                    Ac = A[:, :-1]
+                    b1 = b[:-1]
+                    b2 = np.zeros_like(b1)
+                    b2[0] = -a_0_m1
+                    b2[-1] = -a_m2_m1
+
+                    # s1 and s2 are the solutions of (n-2, n-2) system
+                    s1 = solve_banded((1, 1), Ac, b1, overwrite_ab=False,
+                                      overwrite_b=False, check_finite=False)
+
+                    s2 = solve_banded((1, 1), Ac, b2, overwrite_ab=False,
+                                      overwrite_b=False, check_finite=False)
+
+                    # computing the s[n-2] solution:
+                    s_m1 = ((b[-1] - a_m1_0 * s1[0] - a_m1_m2 * s1[-1]) /
+                            (a_m1_m1 + a_m1_0 * s2[0] + a_m1_m2 * s2[-1]))
+
+                    # s is the solution of the (n, n) system:
+                    s = np.empty((n,) + y.shape[1:], dtype=y.dtype)
+                    s[:-2] = s1 + s_m1 * s2
+                    s[-2] = s_m1
+                    s[-1] = s[0]
+                else:
+                    if bc_start == 'not-a-knot':
+                        A[1, 0] = dx[1]
+                        A[0, 1] = x[2] - x[0]
+                        d = x[2] - x[0]
+                        b[0] = ((dxr[0] + 2*d) * dxr[1] * slope[0] +
+                                dxr[0]**2 * slope[1]) / d
+                    elif bc_start[0] == 1:
+                        A[1, 0] = 1
+                        A[0, 1] = 0
+                        b[0] = bc_start[1]
+                    elif bc_start[0] == 2:
+                        A[1, 0] = 2 * dx[0]
+                        A[0, 1] = dx[0]
+                        b[0] = -0.5 * bc_start[1] * dx[0]**2 + 3 * (y[1] - y[0])
+
+                    if bc_end == 'not-a-knot':
+                        A[1, -1] = dx[-2]
+                        A[-1, -2] = x[-1] - x[-3]
+                        d = x[-1] - x[-3]
+                        b[-1] = ((dxr[-1]**2*slope[-2] +
+                                 (2*d + dxr[-1])*dxr[-2]*slope[-1]) / d)
+                    elif bc_end[0] == 1:
+                        A[1, -1] = 1
+                        A[-1, -2] = 0
+                        b[-1] = bc_end[1]
+                    elif bc_end[0] == 2:
+                        A[1, -1] = 2 * dx[-1]
+                        A[-1, -2] = dx[-1]
+                        b[-1] = 0.5 * bc_end[1] * dx[-1]**2 + 3 * (y[-1] - y[-2])
+
+                    s = solve_banded((1, 1), A, b, overwrite_ab=True,
+                                     overwrite_b=True, check_finite=False)
+
+        super().__init__(x, y, s, axis=0, extrapolate=extrapolate)
+        self.axis = axis
+
+    @staticmethod
+    def _validate_bc(bc_type, y, expected_deriv_shape, axis):
+        """Validate and prepare boundary conditions.
+
+        Returns
+        -------
+        validated_bc : 2-tuple
+            Boundary conditions for a curve start and end.
+        y : ndarray
+            y casted to complex dtype if one of the boundary conditions has
+            complex dtype.
+        """
+        if isinstance(bc_type, str):
+            if bc_type == 'periodic':
+                if not np.allclose(y[0], y[-1], rtol=1e-15, atol=1e-15):
+                    raise ValueError(
+                        f"The first and last `y` point along axis {axis} must "
+                        "be identical (within machine precision) when "
+                        "bc_type='periodic'.")
+
+            bc_type = (bc_type, bc_type)
+
+        else:
+            if len(bc_type) != 2:
+                raise ValueError("`bc_type` must contain 2 elements to "
+                                 "specify start and end conditions.")
+
+            if 'periodic' in bc_type:
+                raise ValueError("'periodic' `bc_type` is defined for both "
+                                 "curve ends and cannot be used with other "
+                                 "boundary conditions.")
+
+        validated_bc = []
+        for bc in bc_type:
+            if isinstance(bc, str):
+                if bc == 'clamped':
+                    validated_bc.append((1, np.zeros(expected_deriv_shape)))
+                elif bc == 'natural':
+                    validated_bc.append((2, np.zeros(expected_deriv_shape)))
+                elif bc in ['not-a-knot', 'periodic']:
+                    validated_bc.append(bc)
+                else:
+                    raise ValueError(f"bc_type={bc} is not allowed.")
+            else:
+                try:
+                    deriv_order, deriv_value = bc
+                except Exception as e:
+                    raise ValueError(
+                        "A specified derivative value must be "
+                        "given in the form (order, value)."
+                    ) from e
+
+                if deriv_order not in [1, 2]:
+                    raise ValueError("The specified derivative order must "
+                                     "be 1 or 2.")
+
+                deriv_value = np.asarray(deriv_value)
+                if deriv_value.shape != expected_deriv_shape:
+                    raise ValueError(
+                        "`deriv_value` shape {} is not the expected one {}."
+                        .format(deriv_value.shape, expected_deriv_shape))
+
+                if np.issubdtype(deriv_value.dtype, np.complexfloating):
+                    y = y.astype(complex, copy=False)
+
+                validated_bc.append((deriv_order, deriv_value))
+
+        return validated_bc, y

venv/lib/python3.10/site-packages/scipy/interpolate/_fitpack2.py

@@ -0,0 +1,2362 @@
+"""
+fitpack --- curve and surface fitting with splines
+
+fitpack is based on a collection of Fortran routines DIERCKX
+by P. Dierckx (see http://www.netlib.org/dierckx/) transformed
+to double routines by Pearu Peterson.
+"""
+# Created by Pearu Peterson, June,August 2003
+__all__ = [
+    'UnivariateSpline',
+    'InterpolatedUnivariateSpline',
+    'LSQUnivariateSpline',
+    'BivariateSpline',
+    'LSQBivariateSpline',
+    'SmoothBivariateSpline',
+    'LSQSphereBivariateSpline',
+    'SmoothSphereBivariateSpline',
+    'RectBivariateSpline',
+    'RectSphereBivariateSpline']
+
+
+import warnings
+
+from numpy import zeros, concatenate, ravel, diff, array, ones  # noqa:F401
+import numpy as np
+
+from . import _fitpack_impl
+from . import dfitpack
+
+
+dfitpack_int = dfitpack.types.intvar.dtype
+
+
+# ############### Univariate spline ####################
+
+_curfit_messages = {1: """
+The required storage space exceeds the available storage space, as
+specified by the parameter nest: nest too small. If nest is already
+large (say nest > m/2), it may also indicate that s is too small.
+The approximation returned is the weighted least-squares spline
+according to the knots t[0],t[1],...,t[n-1]. (n=nest) the parameter fp
+gives the corresponding weighted sum of squared residuals (fp>s).
+""",
+                    2: """
+A theoretically impossible result was found during the iteration
+process for finding a smoothing spline with fp = s: s too small.
+There is an approximation returned but the corresponding weighted sum
+of squared residuals does not satisfy the condition abs(fp-s)/s < tol.""",
+                    3: """
+The maximal number of iterations maxit (set to 20 by the program)
+allowed for finding a smoothing spline with fp=s has been reached: s
+too small.
+There is an approximation returned but the corresponding weighted sum
+of squared residuals does not satisfy the condition abs(fp-s)/s < tol.""",
+                    10: """
+Error on entry, no approximation returned. The following conditions
+must hold:
+xb<=x[0]<x[1]<...<x[m-1]<=xe, w[i]>0, i=0..m-1
+if iopt=-1:
+  xb<t[k+1]<t[k+2]<...<t[n-k-2]<xe"""
+                    }
+
+
+# UnivariateSpline, ext parameter can be an int or a string
+_extrap_modes = {0: 0, 'extrapolate': 0,
+                 1: 1, 'zeros': 1,
+                 2: 2, 'raise': 2,
+                 3: 3, 'const': 3}
+
+
+class UnivariateSpline:
+    """
+    1-D smoothing spline fit to a given set of data points.
+
+    Fits a spline y = spl(x) of degree `k` to the provided `x`, `y` data.  `s`
+    specifies the number of knots by specifying a smoothing condition.
+
+    Parameters
+    ----------
+    x : (N,) array_like
+        1-D array of independent input data. Must be increasing;
+        must be strictly increasing if `s` is 0.
+    y : (N,) array_like
+        1-D array of dependent input data, of the same length as `x`.
+    w : (N,) array_like, optional
+        Weights for spline fitting.  Must be positive.  If `w` is None,
+        weights are all 1. Default is None.
+    bbox : (2,) array_like, optional
+        2-sequence specifying the boundary of the approximation interval. If
+        `bbox` is None, ``bbox=[x[0], x[-1]]``. Default is None.
+    k : int, optional
+        Degree of the smoothing spline.  Must be 1 <= `k` <= 5.
+        ``k = 3`` is a cubic spline. Default is 3.
+    s : float or None, optional
+        Positive smoothing factor used to choose the number of knots.  Number
+        of knots will be increased until the smoothing condition is satisfied::
+
+            sum((w[i] * (y[i]-spl(x[i])))**2, axis=0) <= s
+
+        However, because of numerical issues, the actual condition is::
+
+            abs(sum((w[i] * (y[i]-spl(x[i])))**2, axis=0) - s) < 0.001 * s
+
+        If `s` is None, `s` will be set as `len(w)` for a smoothing spline
+        that uses all data points.
+        If 0, spline will interpolate through all data points. This is
+        equivalent to `InterpolatedUnivariateSpline`.
+        Default is None.
+        The user can use the `s` to control the tradeoff between closeness
+        and smoothness of fit. Larger `s` means more smoothing while smaller
+        values of `s` indicate less smoothing.
+        Recommended values of `s` depend on the weights, `w`. If the weights
+        represent the inverse of the standard-deviation of `y`, then a good
+        `s` value should be found in the range (m-sqrt(2*m),m+sqrt(2*m))
+        where m is the number of datapoints in `x`, `y`, and `w`. This means
+        ``s = len(w)`` should be a good value if ``1/w[i]`` is an
+        estimate of the standard deviation of ``y[i]``.
+    ext : int or str, optional
+        Controls the extrapolation mode for elements
+        not in the interval defined by the knot sequence.
+
+        * if ext=0 or 'extrapolate', return the extrapolated value.
+        * if ext=1 or 'zeros', return 0
+        * if ext=2 or 'raise', raise a ValueError
+        * if ext=3 or 'const', return the boundary value.
+
+        Default is 0.
+
+    check_finite : bool, optional
+        Whether to check that the input arrays contain only finite numbers.
+        Disabling may give a performance gain, but may result in problems
+        (crashes, non-termination or non-sensical results) if the inputs
+        do contain infinities or NaNs.
+        Default is False.
+
+    See Also
+    --------
+    BivariateSpline :
+        a base class for bivariate splines.
+    SmoothBivariateSpline :
+        a smoothing bivariate spline through the given points
+    LSQBivariateSpline :
+        a bivariate spline using weighted least-squares fitting
+    RectSphereBivariateSpline :
+        a bivariate spline over a rectangular mesh on a sphere
+    SmoothSphereBivariateSpline :
+        a smoothing bivariate spline in spherical coordinates
+    LSQSphereBivariateSpline :
+        a bivariate spline in spherical coordinates using weighted
+        least-squares fitting
+    RectBivariateSpline :
+        a bivariate spline over a rectangular mesh
+    InterpolatedUnivariateSpline :
+        a interpolating univariate spline for a given set of data points.
+    bisplrep :
+        a function to find a bivariate B-spline representation of a surface
+    bisplev :
+        a function to evaluate a bivariate B-spline and its derivatives
+    splrep :
+        a function to find the B-spline representation of a 1-D curve
+    splev :
+        a function to evaluate a B-spline or its derivatives
+    sproot :
+        a function to find the roots of a cubic B-spline
+    splint :
+        a function to evaluate the definite integral of a B-spline between two
+        given points
+    spalde :
+        a function to evaluate all derivatives of a B-spline
+
+    Notes
+    -----
+    The number of data points must be larger than the spline degree `k`.
+
+    **NaN handling**: If the input arrays contain ``nan`` values, the result
+    is not useful, since the underlying spline fitting routines cannot deal
+    with ``nan``. A workaround is to use zero weights for not-a-number
+    data points:
+
+    >>> import numpy as np
+    >>> from scipy.interpolate import UnivariateSpline
+    >>> x, y = np.array([1, 2, 3, 4]), np.array([1, np.nan, 3, 4])
+    >>> w = np.isnan(y)
+    >>> y[w] = 0.
+    >>> spl = UnivariateSpline(x, y, w=~w)
+
+    Notice the need to replace a ``nan`` by a numerical value (precise value
+    does not matter as long as the corresponding weight is zero.)
+
+    References
+    ----------
+    Based on algorithms described in [1]_, [2]_, [3]_, and [4]_:
+
+    .. [1] P. Dierckx, "An algorithm for smoothing, differentiation and
+       integration of experimental data using spline functions",
+       J.Comp.Appl.Maths 1 (1975) 165-184.
+    .. [2] P. Dierckx, "A fast algorithm for smoothing data on a rectangular
+       grid while using spline functions", SIAM J.Numer.Anal. 19 (1982)
+       1286-1304.
+    .. [3] P. Dierckx, "An improved algorithm for curve fitting with spline
+       functions", report tw54, Dept. Computer Science,K.U. Leuven, 1981.
+    .. [4] P. Dierckx, "Curve and surface fitting with splines", Monographs on
+       Numerical Analysis, Oxford University Press, 1993.
+
+    Examples
+    --------
+    >>> import numpy as np
+    >>> import matplotlib.pyplot as plt
+    >>> from scipy.interpolate import UnivariateSpline
+    >>> rng = np.random.default_rng()
+    >>> x = np.linspace(-3, 3, 50)
+    >>> y = np.exp(-x**2) + 0.1 * rng.standard_normal(50)
+    >>> plt.plot(x, y, 'ro', ms=5)
+
+    Use the default value for the smoothing parameter:
+
+    >>> spl = UnivariateSpline(x, y)
+    >>> xs = np.linspace(-3, 3, 1000)
+    >>> plt.plot(xs, spl(xs), 'g', lw=3)
+
+    Manually change the amount of smoothing:
+
+    >>> spl.set_smoothing_factor(0.5)
+    >>> plt.plot(xs, spl(xs), 'b', lw=3)
+    >>> plt.show()
+
+    """
+
+    def __init__(self, x, y, w=None, bbox=[None]*2, k=3, s=None,
+                 ext=0, check_finite=False):
+
+        x, y, w, bbox, self.ext = self.validate_input(x, y, w, bbox, k, s, ext,
+                                                      check_finite)
+
+        # _data == x,y,w,xb,xe,k,s,n,t,c,fp,fpint,nrdata,ier
+        data = dfitpack.fpcurf0(x, y, k, w=w, xb=bbox[0],
+                                xe=bbox[1], s=s)
+        if data[-1] == 1:
+            # nest too small, setting to maximum bound
+            data = self._reset_nest(data)
+        self._data = data
+        self._reset_class()
+
+    @staticmethod
+    def validate_input(x, y, w, bbox, k, s, ext, check_finite):
+        x, y, bbox = np.asarray(x), np.asarray(y), np.asarray(bbox)
+        if w is not None:
+            w = np.asarray(w)
+        if check_finite:
+            w_finite = np.isfinite(w).all() if w is not None else True
+            if (not np.isfinite(x).all() or not np.isfinite(y).all() or
+                    not w_finite):
+                raise ValueError("x and y array must not contain "
+                                 "NaNs or infs.")
+        if s is None or s > 0:
+            if not np.all(diff(x) >= 0.0):
+                raise ValueError("x must be increasing if s > 0")
+        else:
+            if not np.all(diff(x) > 0.0):
+                raise ValueError("x must be strictly increasing if s = 0")
+        if x.size != y.size:
+            raise ValueError("x and y should have a same length")
+        elif w is not None and not x.size == y.size == w.size:
+            raise ValueError("x, y, and w should have a same length")
+        elif bbox.shape != (2,):
+            raise ValueError("bbox shape should be (2,)")
+        elif not (1 <= k <= 5):
+            raise ValueError("k should be 1 <= k <= 5")
+        elif s is not None and not s >= 0.0:
+            raise ValueError("s should be s >= 0.0")
+
+        try:
+            ext = _extrap_modes[ext]
+        except KeyError as e:
+            raise ValueError("Unknown extrapolation mode %s." % ext) from e
+
+        return x, y, w, bbox, ext
+
+    @classmethod
+    def _from_tck(cls, tck, ext=0):
+        """Construct a spline object from given tck"""
+        self = cls.__new__(cls)
+        t, c, k = tck
+        self._eval_args = tck
+        # _data == x,y,w,xb,xe,k,s,n,t,c,fp,fpint,nrdata,ier
+        self._data = (None, None, None, None, None, k, None, len(t), t,
+                      c, None, None, None, None)
+        self.ext = ext
+        return self
+
+    def _reset_class(self):
+        data = self._data
+        n, t, c, k, ier = data[7], data[8], data[9], data[5], data[-1]
+        self._eval_args = t[:n], c[:n], k
+        if ier == 0:
+            # the spline returned has a residual sum of squares fp
+            # such that abs(fp-s)/s <= tol with tol a relative
+            # tolerance set to 0.001 by the program
+            pass
+        elif ier == -1:
+            # the spline returned is an interpolating spline
+            self._set_class(InterpolatedUnivariateSpline)
+        elif ier == -2:
+            # the spline returned is the weighted least-squares
+            # polynomial of degree k. In this extreme case fp gives
+            # the upper bound fp0 for the smoothing factor s.
+            self._set_class(LSQUnivariateSpline)
+        else:
+            # error
+            if ier == 1:
+                self._set_class(LSQUnivariateSpline)
+            message = _curfit_messages.get(ier, 'ier=%s' % (ier))
+            warnings.warn(message, stacklevel=3)
+
+    def _set_class(self, cls):
+        self._spline_class = cls
+        if self.__class__ in (UnivariateSpline, InterpolatedUnivariateSpline,
+                              LSQUnivariateSpline):
+            self.__class__ = cls
+        else:
+            # It's an unknown subclass -- don't change class. cf. #731
+            pass
+
+    def _reset_nest(self, data, nest=None):
+        n = data[10]
+        if nest is None:
+            k, m = data[5], len(data[0])
+            nest = m+k+1  # this is the maximum bound for nest
+        else:
+            if not n <= nest:
+                raise ValueError("`nest` can only be increased")
+        t, c, fpint, nrdata = (np.resize(data[j], nest) for j in
+                               [8, 9, 11, 12])
+
+        args = data[:8] + (t, c, n, fpint, nrdata, data[13])
+        data = dfitpack.fpcurf1(*args)
+        return data
+
+    def set_smoothing_factor(self, s):
+        """ Continue spline computation with the given smoothing
+        factor s and with the knots found at the last call.
+
+        This routine modifies the spline in place.
+
+        """
+        data = self._data
+        if data[6] == -1:
+            warnings.warn('smoothing factor unchanged for'
+                          'LSQ spline with fixed knots',
+                          stacklevel=2)
+            return
+        args = data[:6] + (s,) + data[7:]
+        data = dfitpack.fpcurf1(*args)
+        if data[-1] == 1:
+            # nest too small, setting to maximum bound
+            data = self._reset_nest(data)
+        self._data = data
+        self._reset_class()
+
+    def __call__(self, x, nu=0, ext=None):
+        """
+        Evaluate spline (or its nu-th derivative) at positions x.
+
+        Parameters
+        ----------
+        x : array_like
+            A 1-D array of points at which to return the value of the smoothed
+            spline or its derivatives. Note: `x` can be unordered but the
+            evaluation is more efficient if `x` is (partially) ordered.
+        nu  : int
+            The order of derivative of the spline to compute.
+        ext : int
+            Controls the value returned for elements of `x` not in the
+            interval defined by the knot sequence.
+
+            * if ext=0 or 'extrapolate', return the extrapolated value.
+            * if ext=1 or 'zeros', return 0
+            * if ext=2 or 'raise', raise a ValueError
+            * if ext=3 or 'const', return the boundary value.
+
+            The default value is 0, passed from the initialization of
+            UnivariateSpline.
+
+        """
+        x = np.asarray(x)
+        # empty input yields empty output
+        if x.size == 0:
+            return array([])
+        if ext is None:
+            ext = self.ext
+        else:
+            try:
+                ext = _extrap_modes[ext]
+            except KeyError as e:
+                raise ValueError("Unknown extrapolation mode %s." % ext) from e
+        return _fitpack_impl.splev(x, self._eval_args, der=nu, ext=ext)
+
+    def get_knots(self):
+        """ Return positions of interior knots of the spline.
+
+        Internally, the knot vector contains ``2*k`` additional boundary knots.
+        """
+        data = self._data
+        k, n = data[5], data[7]
+        return data[8][k:n-k]
+
+    def get_coeffs(self):
+        """Return spline coefficients."""
+        data = self._data
+        k, n = data[5], data[7]
+        return data[9][:n-k-1]
+
+    def get_residual(self):
+        """Return weighted sum of squared residuals of the spline approximation.
+
+           This is equivalent to::
+
+                sum((w[i] * (y[i]-spl(x[i])))**2, axis=0)
+
+        """
+        return self._data[10]
+
+    def integral(self, a, b):
+        """ Return definite integral of the spline between two given points.
+
+        Parameters
+        ----------
+        a : float
+            Lower limit of integration.
+        b : float
+            Upper limit of integration.
+
+        Returns
+        -------
+        integral : float
+            The value of the definite integral of the spline between limits.
+
+        Examples
+        --------
+        >>> import numpy as np
+        >>> from scipy.interpolate import UnivariateSpline
+        >>> x = np.linspace(0, 3, 11)
+        >>> y = x**2
+        >>> spl = UnivariateSpline(x, y)
+        >>> spl.integral(0, 3)
+        9.0
+
+        which agrees with :math:`\\int x^2 dx = x^3 / 3` between the limits
+        of 0 and 3.
+
+        A caveat is that this routine assumes the spline to be zero outside of
+        the data limits:
+
+        >>> spl.integral(-1, 4)
+        9.0
+        >>> spl.integral(-1, 0)
+        0.0
+
+        """
+        return _fitpack_impl.splint(a, b, self._eval_args)
+
+    def derivatives(self, x):
+        """ Return all derivatives of the spline at the point x.
+
+        Parameters
+        ----------
+        x : float
+            The point to evaluate the derivatives at.
+
+        Returns
+        -------
+        der : ndarray, shape(k+1,)
+            Derivatives of the orders 0 to k.
+
+        Examples
+        --------
+        >>> import numpy as np
+        >>> from scipy.interpolate import UnivariateSpline
+        >>> x = np.linspace(0, 3, 11)
+        >>> y = x**2
+        >>> spl = UnivariateSpline(x, y)
+        >>> spl.derivatives(1.5)
+        array([2.25, 3.0, 2.0, 0])
+
+        """
+        return _fitpack_impl.spalde(x, self._eval_args)
+
+    def roots(self):
+        """ Return the zeros of the spline.
+
+        Notes
+        -----
+        Restriction: only cubic splines are supported by FITPACK. For non-cubic
+        splines, use `PPoly.root` (see below for an example).
+
+        Examples
+        --------
+
+        For some data, this method may miss a root. This happens when one of
+        the spline knots (which FITPACK places automatically) happens to
+        coincide with the true root. A workaround is to convert to `PPoly`,
+        which uses a different root-finding algorithm.
+
+        For example,
+
+        >>> x = [1.96, 1.97, 1.98, 1.99, 2.00, 2.01, 2.02, 2.03, 2.04, 2.05]
+        >>> y = [-6.365470e-03, -4.790580e-03, -3.204320e-03, -1.607270e-03,
+        ...      4.440892e-16,  1.616930e-03,  3.243000e-03,  4.877670e-03,
+        ...      6.520430e-03,  8.170770e-03]
+        >>> from scipy.interpolate import UnivariateSpline
+        >>> spl = UnivariateSpline(x, y, s=0)
+        >>> spl.roots()
+        array([], dtype=float64)
+
+        Converting to a PPoly object does find the roots at `x=2`:
+
+        >>> from scipy.interpolate import splrep, PPoly
+        >>> tck = splrep(x, y, s=0)
+        >>> ppoly = PPoly.from_spline(tck)
+        >>> ppoly.roots(extrapolate=False)
+        array([2.])
+
+        See Also
+        --------
+        sproot
+        PPoly.roots
+
+        """
+        k = self._data[5]
+        if k == 3:
+            t = self._eval_args[0]
+            mest = 3 * (len(t) - 7)
+            return _fitpack_impl.sproot(self._eval_args, mest=mest)
+        raise NotImplementedError('finding roots unsupported for '
+                                  'non-cubic splines')
+
+    def derivative(self, n=1):
+        """
+        Construct a new spline representing the derivative of this spline.
+
+        Parameters
+        ----------
+        n : int, optional
+            Order of derivative to evaluate. Default: 1
+
+        Returns
+        -------
+        spline : UnivariateSpline
+            Spline of order k2=k-n representing the derivative of this
+            spline.
+
+        See Also
+        --------
+        splder, antiderivative
+
+        Notes
+        -----
+
+        .. versionadded:: 0.13.0
+
+        Examples
+        --------
+        This can be used for finding maxima of a curve:
+
+        >>> import numpy as np
+        >>> from scipy.interpolate import UnivariateSpline
+        >>> x = np.linspace(0, 10, 70)
+        >>> y = np.sin(x)
+        >>> spl = UnivariateSpline(x, y, k=4, s=0)
+
+        Now, differentiate the spline and find the zeros of the
+        derivative. (NB: `sproot` only works for order 3 splines, so we
+        fit an order 4 spline):
+
+        >>> spl.derivative().roots() / np.pi
+        array([ 0.50000001,  1.5       ,  2.49999998])
+
+        This agrees well with roots :math:`\\pi/2 + n\\pi` of
+        :math:`\\cos(x) = \\sin'(x)`.
+
+        """
+        tck = _fitpack_impl.splder(self._eval_args, n)
+        # if self.ext is 'const', derivative.ext will be 'zeros'
+        ext = 1 if self.ext == 3 else self.ext
+        return UnivariateSpline._from_tck(tck, ext=ext)
+
+    def antiderivative(self, n=1):
+        """
+        Construct a new spline representing the antiderivative of this spline.
+
+        Parameters
+        ----------
+        n : int, optional
+            Order of antiderivative to evaluate. Default: 1
+
+        Returns
+        -------
+        spline : UnivariateSpline
+            Spline of order k2=k+n representing the antiderivative of this
+            spline.
+
+        Notes
+        -----
+
+        .. versionadded:: 0.13.0
+
+        See Also
+        --------
+        splantider, derivative
+
+        Examples
+        --------
+        >>> import numpy as np
+        >>> from scipy.interpolate import UnivariateSpline
+        >>> x = np.linspace(0, np.pi/2, 70)
+        >>> y = 1 / np.sqrt(1 - 0.8*np.sin(x)**2)
+        >>> spl = UnivariateSpline(x, y, s=0)
+
+        The derivative is the inverse operation of the antiderivative,
+        although some floating point error accumulates:
+
+        >>> spl(1.7), spl.antiderivative().derivative()(1.7)
+        (array(2.1565429877197317), array(2.1565429877201865))
+
+        Antiderivative can be used to evaluate definite integrals:
+
+        >>> ispl = spl.antiderivative()
+        >>> ispl(np.pi/2) - ispl(0)
+        2.2572053588768486
+
+        This is indeed an approximation to the complete elliptic integral
+        :math:`K(m) = \\int_0^{\\pi/2} [1 - m\\sin^2 x]^{-1/2} dx`:
+
+        >>> from scipy.special import ellipk
+        >>> ellipk(0.8)
+        2.2572053268208538
+
+        """
+        tck = _fitpack_impl.splantider(self._eval_args, n)
+        return UnivariateSpline._from_tck(tck, self.ext)
+
+
+class InterpolatedUnivariateSpline(UnivariateSpline):
+    """
+    1-D interpolating spline for a given set of data points.
+
+    Fits a spline y = spl(x) of degree `k` to the provided `x`, `y` data.
+    Spline function passes through all provided points. Equivalent to
+    `UnivariateSpline` with  `s` = 0.
+
+    Parameters
+    ----------
+    x : (N,) array_like
+        Input dimension of data points -- must be strictly increasing
+    y : (N,) array_like
+        input dimension of data points
+    w : (N,) array_like, optional
+        Weights for spline fitting.  Must be positive.  If None (default),
+        weights are all 1.
+    bbox : (2,) array_like, optional
+        2-sequence specifying the boundary of the approximation interval. If
+        None (default), ``bbox=[x[0], x[-1]]``.
+    k : int, optional
+        Degree of the smoothing spline.  Must be ``1 <= k <= 5``. Default is
+        ``k = 3``, a cubic spline.
+    ext : int or str, optional
+        Controls the extrapolation mode for elements
+        not in the interval defined by the knot sequence.
+
+        * if ext=0 or 'extrapolate', return the extrapolated value.
+        * if ext=1 or 'zeros', return 0
+        * if ext=2 or 'raise', raise a ValueError
+        * if ext=3 of 'const', return the boundary value.
+
+        The default value is 0.
+
+    check_finite : bool, optional
+        Whether to check that the input arrays contain only finite numbers.
+        Disabling may give a performance gain, but may result in problems
+        (crashes, non-termination or non-sensical results) if the inputs
+        do contain infinities or NaNs.
+        Default is False.
+
+    See Also
+    --------
+    UnivariateSpline :
+        a smooth univariate spline to fit a given set of data points.
+    LSQUnivariateSpline :
+        a spline for which knots are user-selected
+    SmoothBivariateSpline :
+        a smoothing bivariate spline through the given points
+    LSQBivariateSpline :
+        a bivariate spline using weighted least-squares fitting
+    splrep :
+        a function to find the B-spline representation of a 1-D curve
+    splev :
+        a function to evaluate a B-spline or its derivatives
+    sproot :
+        a function to find the roots of a cubic B-spline
+    splint :
+        a function to evaluate the definite integral of a B-spline between two
+        given points
+    spalde :
+        a function to evaluate all derivatives of a B-spline
+
+    Notes
+    -----
+    The number of data points must be larger than the spline degree `k`.
+
+    Examples
+    --------
+    >>> import numpy as np
+    >>> import matplotlib.pyplot as plt
+    >>> from scipy.interpolate import InterpolatedUnivariateSpline
+    >>> rng = np.random.default_rng()
+    >>> x = np.linspace(-3, 3, 50)
+    >>> y = np.exp(-x**2) + 0.1 * rng.standard_normal(50)
+    >>> spl = InterpolatedUnivariateSpline(x, y)
+    >>> plt.plot(x, y, 'ro', ms=5)
+    >>> xs = np.linspace(-3, 3, 1000)
+    >>> plt.plot(xs, spl(xs), 'g', lw=3, alpha=0.7)
+    >>> plt.show()
+
+    Notice that the ``spl(x)`` interpolates `y`:
+
+    >>> spl.get_residual()
+    0.0
+
+    """
+
+    def __init__(self, x, y, w=None, bbox=[None]*2, k=3,
+                 ext=0, check_finite=False):
+
+        x, y, w, bbox, self.ext = self.validate_input(x, y, w, bbox, k, None,
+                                            ext, check_finite)
+        if not np.all(diff(x) > 0.0):
+            raise ValueError('x must be strictly increasing')
+
+        # _data == x,y,w,xb,xe,k,s,n,t,c,fp,fpint,nrdata,ier
+        self._data = dfitpack.fpcurf0(x, y, k, w=w, xb=bbox[0],
+                                      xe=bbox[1], s=0)
+        self._reset_class()
+
+
+_fpchec_error_string = """The input parameters have been rejected by fpchec. \
+This means that at least one of the following conditions is violated:
+
+1) k+1 <= n-k-1 <= m
+2) t(1) <= t(2) <= ... <= t(k+1)
+   t(n-k) <= t(n-k+1) <= ... <= t(n)
+3) t(k+1) < t(k+2) < ... < t(n-k)
+4) t(k+1) <= x(i) <= t(n-k)
+5) The conditions specified by Schoenberg and Whitney must hold
+   for at least one subset of data points, i.e., there must be a
+   subset of data points y(j) such that
+       t(j) < y(j) < t(j+k+1), j=1,2,...,n-k-1
+"""
+
+
+class LSQUnivariateSpline(UnivariateSpline):
+    """
+    1-D spline with explicit internal knots.
+
+    Fits a spline y = spl(x) of degree `k` to the provided `x`, `y` data.  `t`
+    specifies the internal knots of the spline
+
+    Parameters
+    ----------
+    x : (N,) array_like
+        Input dimension of data points -- must be increasing
+    y : (N,) array_like
+        Input dimension of data points
+    t : (M,) array_like
+        interior knots of the spline.  Must be in ascending order and::
+
+            bbox[0] < t[0] < ... < t[-1] < bbox[-1]
+
+    w : (N,) array_like, optional
+        weights for spline fitting. Must be positive. If None (default),
+        weights are all 1.
+    bbox : (2,) array_like, optional
+        2-sequence specifying the boundary of the approximation interval. If
+        None (default), ``bbox = [x[0], x[-1]]``.
+    k : int, optional
+        Degree of the smoothing spline.  Must be 1 <= `k` <= 5.
+        Default is `k` = 3, a cubic spline.
+    ext : int or str, optional
+        Controls the extrapolation mode for elements
+        not in the interval defined by the knot sequence.
+
+        * if ext=0 or 'extrapolate', return the extrapolated value.
+        * if ext=1 or 'zeros', return 0
+        * if ext=2 or 'raise', raise a ValueError
+        * if ext=3 of 'const', return the boundary value.
+
+        The default value is 0.
+
+    check_finite : bool, optional
+        Whether to check that the input arrays contain only finite numbers.
+        Disabling may give a performance gain, but may result in problems
+        (crashes, non-termination or non-sensical results) if the inputs
+        do contain infinities or NaNs.
+        Default is False.
+
+    Raises
+    ------
+    ValueError
+        If the interior knots do not satisfy the Schoenberg-Whitney conditions
+
+    See Also
+    --------
+    UnivariateSpline :
+        a smooth univariate spline to fit a given set of data points.
+    InterpolatedUnivariateSpline :
+        a interpolating univariate spline for a given set of data points.
+    splrep :
+        a function to find the B-spline representation of a 1-D curve
+    splev :
+        a function to evaluate a B-spline or its derivatives
+    sproot :
+        a function to find the roots of a cubic B-spline
+    splint :
+        a function to evaluate the definite integral of a B-spline between two
+        given points
+    spalde :
+        a function to evaluate all derivatives of a B-spline
+
+    Notes
+    -----
+    The number of data points must be larger than the spline degree `k`.
+
+    Knots `t` must satisfy the Schoenberg-Whitney conditions,
+    i.e., there must be a subset of data points ``x[j]`` such that
+    ``t[j] < x[j] < t[j+k+1]``, for ``j=0, 1,...,n-k-2``.
+
+    Examples
+    --------
+    >>> import numpy as np
+    >>> from scipy.interpolate import LSQUnivariateSpline, UnivariateSpline
+    >>> import matplotlib.pyplot as plt
+    >>> rng = np.random.default_rng()
+    >>> x = np.linspace(-3, 3, 50)
+    >>> y = np.exp(-x**2) + 0.1 * rng.standard_normal(50)
+
+    Fit a smoothing spline with a pre-defined internal knots:
+
+    >>> t = [-1, 0, 1]
+    >>> spl = LSQUnivariateSpline(x, y, t)
+
+    >>> xs = np.linspace(-3, 3, 1000)
+    >>> plt.plot(x, y, 'ro', ms=5)
+    >>> plt.plot(xs, spl(xs), 'g-', lw=3)
+    >>> plt.show()
+
+    Check the knot vector:
+
+    >>> spl.get_knots()
+    array([-3., -1., 0., 1., 3.])
+
+    Constructing lsq spline using the knots from another spline:
+
+    >>> x = np.arange(10)
+    >>> s = UnivariateSpline(x, x, s=0)
+    >>> s.get_knots()
+    array([ 0.,  2.,  3.,  4.,  5.,  6.,  7.,  9.])
+    >>> knt = s.get_knots()
+    >>> s1 = LSQUnivariateSpline(x, x, knt[1:-1])    # Chop 1st and last knot
+    >>> s1.get_knots()
+    array([ 0.,  2.,  3.,  4.,  5.,  6.,  7.,  9.])
+
+    """
+
+    def __init__(self, x, y, t, w=None, bbox=[None]*2, k=3,
+                 ext=0, check_finite=False):
+
+        x, y, w, bbox, self.ext = self.validate_input(x, y, w, bbox, k, None,
+                                                      ext, check_finite)
+        if not np.all(diff(x) >= 0.0):
+            raise ValueError('x must be increasing')
+
+        # _data == x,y,w,xb,xe,k,s,n,t,c,fp,fpint,nrdata,ier
+        xb = bbox[0]
+        xe = bbox[1]
+        if xb is None:
+            xb = x[0]
+        if xe is None:
+            xe = x[-1]
+        t = concatenate(([xb]*(k+1), t, [xe]*(k+1)))
+        n = len(t)
+        if not np.all(t[k+1:n-k]-t[k:n-k-1] > 0, axis=0):
+            raise ValueError('Interior knots t must satisfy '
+                             'Schoenberg-Whitney conditions')
+        if not dfitpack.fpchec(x, t, k) == 0:
+            raise ValueError(_fpchec_error_string)
+        data = dfitpack.fpcurfm1(x, y, k, t, w=w, xb=xb, xe=xe)
+        self._data = data[:-3] + (None, None, data[-1])
+        self._reset_class()
+
+
+# ############### Bivariate spline ####################
+
+class _BivariateSplineBase:
+    """ Base class for Bivariate spline s(x,y) interpolation on the rectangle
+    [xb,xe] x [yb, ye] calculated from a given set of data points
+    (x,y,z).
+
+    See Also
+    --------
+    bisplrep :
+        a function to find a bivariate B-spline representation of a surface
+    bisplev :
+        a function to evaluate a bivariate B-spline and its derivatives
+    BivariateSpline :
+        a base class for bivariate splines.
+    SphereBivariateSpline :
+        a bivariate spline on a spherical grid
+    """
+
+    @classmethod
+    def _from_tck(cls, tck):
+        """Construct a spline object from given tck and degree"""
+        self = cls.__new__(cls)
+        if len(tck) != 5:
+            raise ValueError("tck should be a 5 element tuple of tx,"
+                             " ty, c, kx, ky")
+        self.tck = tck[:3]
+        self.degrees = tck[3:]
+        return self
+
+    def get_residual(self):
+        """ Return weighted sum of squared residuals of the spline
+        approximation: sum ((w[i]*(z[i]-s(x[i],y[i])))**2,axis=0)
+        """
+        return self.fp
+
+    def get_knots(self):
+        """ Return a tuple (tx,ty) where tx,ty contain knots positions
+        of the spline with respect to x-, y-variable, respectively.
+        The position of interior and additional knots are given as
+        t[k+1:-k-1] and t[:k+1]=b, t[-k-1:]=e, respectively.
+        """
+        return self.tck[:2]
+
+    def get_coeffs(self):
+        """ Return spline coefficients."""
+        return self.tck[2]
+
+    def __call__(self, x, y, dx=0, dy=0, grid=True):
+        """
+        Evaluate the spline or its derivatives at given positions.
+
+        Parameters
+        ----------
+        x, y : array_like
+            Input coordinates.
+
+            If `grid` is False, evaluate the spline at points ``(x[i],
+            y[i]), i=0, ..., len(x)-1``.  Standard Numpy broadcasting
+            is obeyed.
+
+            If `grid` is True: evaluate spline at the grid points
+            defined by the coordinate arrays x, y. The arrays must be
+            sorted to increasing order.
+
+            The ordering of axes is consistent with
+            ``np.meshgrid(..., indexing="ij")`` and inconsistent with the
+            default ordering ``np.meshgrid(..., indexing="xy")``.
+        dx : int
+            Order of x-derivative
+
+            .. versionadded:: 0.14.0
+        dy : int
+            Order of y-derivative
+
+            .. versionadded:: 0.14.0
+        grid : bool
+            Whether to evaluate the results on a grid spanned by the
+            input arrays, or at points specified by the input arrays.
+
+            .. versionadded:: 0.14.0
+
+        Examples
+        --------
+        Suppose that we want to bilinearly interpolate an exponentially decaying
+        function in 2 dimensions.
+
+        >>> import numpy as np
+        >>> from scipy.interpolate import RectBivariateSpline
+
+        We sample the function on a coarse grid. Note that the default indexing="xy"
+        of meshgrid would result in an unexpected (transposed) result after
+        interpolation.
+
+        >>> xarr = np.linspace(-3, 3, 100)
+        >>> yarr = np.linspace(-3, 3, 100)
+        >>> xgrid, ygrid = np.meshgrid(xarr, yarr, indexing="ij")
+
+        The function to interpolate decays faster along one axis than the other.
+
+        >>> zdata = np.exp(-np.sqrt((xgrid / 2) ** 2 + ygrid**2))
+
+        Next we sample on a finer grid using interpolation (kx=ky=1 for bilinear).
+
+        >>> rbs = RectBivariateSpline(xarr, yarr, zdata, kx=1, ky=1)
+        >>> xarr_fine = np.linspace(-3, 3, 200)
+        >>> yarr_fine = np.linspace(-3, 3, 200)
+        >>> xgrid_fine, ygrid_fine = np.meshgrid(xarr_fine, yarr_fine, indexing="ij")
+        >>> zdata_interp = rbs(xgrid_fine, ygrid_fine, grid=False)
+
+        And check that the result agrees with the input by plotting both.
+
+        >>> import matplotlib.pyplot as plt
+        >>> fig = plt.figure()
+        >>> ax1 = fig.add_subplot(1, 2, 1, aspect="equal")
+        >>> ax2 = fig.add_subplot(1, 2, 2, aspect="equal")
+        >>> ax1.imshow(zdata)
+        >>> ax2.imshow(zdata_interp)
+        >>> plt.show()
+        """
+        x = np.asarray(x)
+        y = np.asarray(y)
+
+        tx, ty, c = self.tck[:3]
+        kx, ky = self.degrees
+        if grid:
+            if x.size == 0 or y.size == 0:
+                return np.zeros((x.size, y.size), dtype=self.tck[2].dtype)
+
+            if (x.size >= 2) and (not np.all(np.diff(x) >= 0.0)):
+                raise ValueError("x must be strictly increasing when `grid` is True")
+            if (y.size >= 2) and (not np.all(np.diff(y) >= 0.0)):
+                raise ValueError("y must be strictly increasing when `grid` is True")
+
+            if dx or dy:
+                z, ier = dfitpack.parder(tx, ty, c, kx, ky, dx, dy, x, y)
+                if not ier == 0:
+                    raise ValueError("Error code returned by parder: %s" % ier)
+            else:
+                z, ier = dfitpack.bispev(tx, ty, c, kx, ky, x, y)
+                if not ier == 0:
+                    raise ValueError("Error code returned by bispev: %s" % ier)
+        else:
+            # standard Numpy broadcasting
+            if x.shape != y.shape:
+                x, y = np.broadcast_arrays(x, y)
+
+            shape = x.shape
+            x = x.ravel()
+            y = y.ravel()
+
+            if x.size == 0 or y.size == 0:
+                return np.zeros(shape, dtype=self.tck[2].dtype)
+
+            if dx or dy:
+                z, ier = dfitpack.pardeu(tx, ty, c, kx, ky, dx, dy, x, y)
+                if not ier == 0:
+                    raise ValueError("Error code returned by pardeu: %s" % ier)
+            else:
+                z, ier = dfitpack.bispeu(tx, ty, c, kx, ky, x, y)
+                if not ier == 0:
+                    raise ValueError("Error code returned by bispeu: %s" % ier)
+
+            z = z.reshape(shape)
+        return z
+
+    def partial_derivative(self, dx, dy):
+        """Construct a new spline representing a partial derivative of this
+        spline.
+
+        Parameters
+        ----------
+        dx, dy : int
+            Orders of the derivative in x and y respectively. They must be
+            non-negative integers and less than the respective degree of the
+            original spline (self) in that direction (``kx``, ``ky``).
+
+        Returns
+        -------
+        spline :
+            A new spline of degrees (``kx - dx``, ``ky - dy``) representing the
+            derivative of this spline.
+
+        Notes
+        -----
+
+        .. versionadded:: 1.9.0
+
+        """
+        if dx == 0 and dy == 0:
+            return self
+        else:
+            kx, ky = self.degrees
+            if not (dx >= 0 and dy >= 0):
+                raise ValueError("order of derivative must be positive or"
+                                 " zero")
+            if not (dx < kx and dy < ky):
+                raise ValueError("order of derivative must be less than"
+                                 " degree of spline")
+            tx, ty, c = self.tck[:3]
+            newc, ier = dfitpack.pardtc(tx, ty, c, kx, ky, dx, dy)
+            if ier != 0:
+                # This should not happen under normal conditions.
+                raise ValueError("Unexpected error code returned by"
+                                 " pardtc: %d" % ier)
+            nx = len(tx)
+            ny = len(ty)
+            newtx = tx[dx:nx - dx]
+            newty = ty[dy:ny - dy]
+            newkx, newky = kx - dx, ky - dy
+            newclen = (nx - dx - kx - 1) * (ny - dy - ky - 1)
+            return _DerivedBivariateSpline._from_tck((newtx, newty,
+                                                      newc[:newclen],
+                                                      newkx, newky))
+
+
+_surfit_messages = {1: """
+The required storage space exceeds the available storage space: nxest
+or nyest too small, or s too small.
+The weighted least-squares spline corresponds to the current set of
+knots.""",
+                    2: """
+A theoretically impossible result was found during the iteration
+process for finding a smoothing spline with fp = s: s too small or
+badly chosen eps.
+Weighted sum of squared residuals does not satisfy abs(fp-s)/s < tol.""",
+                    3: """
+the maximal number of iterations maxit (set to 20 by the program)
+allowed for finding a smoothing spline with fp=s has been reached:
+s too small.
+Weighted sum of squared residuals does not satisfy abs(fp-s)/s < tol.""",
+                    4: """
+No more knots can be added because the number of b-spline coefficients
+(nx-kx-1)*(ny-ky-1) already exceeds the number of data points m:
+either s or m too small.
+The weighted least-squares spline corresponds to the current set of
+knots.""",
+                    5: """
+No more knots can be added because the additional knot would (quasi)
+coincide with an old one: s too small or too large a weight to an
+inaccurate data point.
+The weighted least-squares spline corresponds to the current set of
+knots.""",
+                    10: """
+Error on entry, no approximation returned. The following conditions
+must hold:
+xb<=x[i]<=xe, yb<=y[i]<=ye, w[i]>0, i=0..m-1
+If iopt==-1, then
+  xb<tx[kx+1]<tx[kx+2]<...<tx[nx-kx-2]<xe
+  yb<ty[ky+1]<ty[ky+2]<...<ty[ny-ky-2]<ye""",
+                    -3: """
+The coefficients of the spline returned have been computed as the
+minimal norm least-squares solution of a (numerically) rank deficient
+system (deficiency=%i). If deficiency is large, the results may be
+inaccurate. Deficiency may strongly depend on the value of eps."""
+                    }
+
+
+class BivariateSpline(_BivariateSplineBase):
+    """
+    Base class for bivariate splines.
+
+    This describes a spline ``s(x, y)`` of degrees ``kx`` and ``ky`` on
+    the rectangle ``[xb, xe] * [yb, ye]`` calculated from a given set
+    of data points ``(x, y, z)``.
+
+    This class is meant to be subclassed, not instantiated directly.
+    To construct these splines, call either `SmoothBivariateSpline` or
+    `LSQBivariateSpline` or `RectBivariateSpline`.
+
+    See Also
+    --------
+    UnivariateSpline :
+        a smooth univariate spline to fit a given set of data points.
+    SmoothBivariateSpline :
+        a smoothing bivariate spline through the given points
+    LSQBivariateSpline :
+        a bivariate spline using weighted least-squares fitting
+    RectSphereBivariateSpline :
+        a bivariate spline over a rectangular mesh on a sphere
+    SmoothSphereBivariateSpline :
+        a smoothing bivariate spline in spherical coordinates
+    LSQSphereBivariateSpline :
+        a bivariate spline in spherical coordinates using weighted
+        least-squares fitting
+    RectBivariateSpline :
+        a bivariate spline over a rectangular mesh.
+    bisplrep :
+        a function to find a bivariate B-spline representation of a surface
+    bisplev :
+        a function to evaluate a bivariate B-spline and its derivatives
+    """
+
+    def ev(self, xi, yi, dx=0, dy=0):
+        """
+        Evaluate the spline at points
+
+        Returns the interpolated value at ``(xi[i], yi[i]),
+        i=0,...,len(xi)-1``.
+
+        Parameters
+        ----------
+        xi, yi : array_like
+            Input coordinates. Standard Numpy broadcasting is obeyed.
+            The ordering of axes is consistent with
+            ``np.meshgrid(..., indexing="ij")`` and inconsistent with the
+            default ordering ``np.meshgrid(..., indexing="xy")``.
+        dx : int, optional
+            Order of x-derivative
+
+            .. versionadded:: 0.14.0
+        dy : int, optional
+            Order of y-derivative
+
+            .. versionadded:: 0.14.0
+
+        Examples
+        --------
+        Suppose that we want to bilinearly interpolate an exponentially decaying
+        function in 2 dimensions.
+
+        >>> import numpy as np
+        >>> from scipy.interpolate import RectBivariateSpline
+        >>> def f(x, y):
+        ...     return np.exp(-np.sqrt((x / 2) ** 2 + y**2))
+
+        We sample the function on a coarse grid and set up the interpolator. Note that
+        the default ``indexing="xy"`` of meshgrid would result in an unexpected
+        (transposed) result after interpolation.
+
+        >>> xarr = np.linspace(-3, 3, 21)
+        >>> yarr = np.linspace(-3, 3, 21)
+        >>> xgrid, ygrid = np.meshgrid(xarr, yarr, indexing="ij")
+        >>> zdata = f(xgrid, ygrid)
+        >>> rbs = RectBivariateSpline(xarr, yarr, zdata, kx=1, ky=1)
+
+        Next we sample the function along a diagonal slice through the coordinate space
+        on a finer grid using interpolation.
+
+        >>> xinterp = np.linspace(-3, 3, 201)
+        >>> yinterp = np.linspace(3, -3, 201)
+        >>> zinterp = rbs.ev(xinterp, yinterp)
+
+        And check that the interpolation passes through the function evaluations as a
+        function of the distance from the origin along the slice.
+
+        >>> import matplotlib.pyplot as plt
+        >>> fig = plt.figure()
+        >>> ax1 = fig.add_subplot(1, 1, 1)
+        >>> ax1.plot(np.sqrt(xarr**2 + yarr**2), np.diag(zdata), "or")
+        >>> ax1.plot(np.sqrt(xinterp**2 + yinterp**2), zinterp, "-b")
+        >>> plt.show()
+        """
+        return self.__call__(xi, yi, dx=dx, dy=dy, grid=False)
+
+    def integral(self, xa, xb, ya, yb):
+        """
+        Evaluate the integral of the spline over area [xa,xb] x [ya,yb].
+
+        Parameters
+        ----------
+        xa, xb : float
+            The end-points of the x integration interval.
+        ya, yb : float
+            The end-points of the y integration interval.
+
+        Returns
+        -------
+        integ : float
+            The value of the resulting integral.
+
+        """
+        tx, ty, c = self.tck[:3]
+        kx, ky = self.degrees
+        return dfitpack.dblint(tx, ty, c, kx, ky, xa, xb, ya, yb)
+
+    @staticmethod
+    def _validate_input(x, y, z, w, kx, ky, eps):
+        x, y, z = np.asarray(x), np.asarray(y), np.asarray(z)
+        if not x.size == y.size == z.size:
+            raise ValueError('x, y, and z should have a same length')
+
+        if w is not None:
+            w = np.asarray(w)
+            if x.size != w.size:
+                raise ValueError('x, y, z, and w should have a same length')
+            elif not np.all(w >= 0.0):
+                raise ValueError('w should be positive')
+        if (eps is not None) and (not 0.0 < eps < 1.0):
+            raise ValueError('eps should be between (0, 1)')
+        if not x.size >= (kx + 1) * (ky + 1):
+            raise ValueError('The length of x, y and z should be at least'
+                             ' (kx+1) * (ky+1)')
+        return x, y, z, w
+
+
+class _DerivedBivariateSpline(_BivariateSplineBase):
+    """Bivariate spline constructed from the coefficients and knots of another
+    spline.
+
+    Notes
+    -----
+    The class is not meant to be instantiated directly from the data to be
+    interpolated or smoothed. As a result, its ``fp`` attribute and
+    ``get_residual`` method are inherited but overridden; ``AttributeError`` is
+    raised when they are accessed.
+
+    The other inherited attributes can be used as usual.
+    """
+    _invalid_why = ("is unavailable, because _DerivedBivariateSpline"
+                    " instance is not constructed from data that are to be"
+                    " interpolated or smoothed, but derived from the"
+                    " underlying knots and coefficients of another spline"
+                    " object")
+
+    @property
+    def fp(self):
+        raise AttributeError("attribute \"fp\" %s" % self._invalid_why)
+
+    def get_residual(self):
+        raise AttributeError("method \"get_residual\" %s" % self._invalid_why)
+
+
+class SmoothBivariateSpline(BivariateSpline):
+    """
+    Smooth bivariate spline approximation.
+
+    Parameters
+    ----------
+    x, y, z : array_like
+        1-D sequences of data points (order is not important).
+    w : array_like, optional
+        Positive 1-D sequence of weights, of same length as `x`, `y` and `z`.
+    bbox : array_like, optional
+        Sequence of length 4 specifying the boundary of the rectangular
+        approximation domain.  By default,
+        ``bbox=[min(x), max(x), min(y), max(y)]``.
+    kx, ky : ints, optional
+        Degrees of the bivariate spline. Default is 3.
+    s : float, optional
+        Positive smoothing factor defined for estimation condition:
+        ``sum((w[i]*(z[i]-s(x[i], y[i])))**2, axis=0) <= s``
+        Default ``s=len(w)`` which should be a good value if ``1/w[i]`` is an
+        estimate of the standard deviation of ``z[i]``.
+    eps : float, optional
+        A threshold for determining the effective rank of an over-determined
+        linear system of equations. `eps` should have a value within the open
+        interval ``(0, 1)``, the default is 1e-16.
+
+    See Also
+    --------
+    BivariateSpline :
+        a base class for bivariate splines.
+    UnivariateSpline :
+        a smooth univariate spline to fit a given set of data points.
+    LSQBivariateSpline :
+        a bivariate spline using weighted least-squares fitting
+    RectSphereBivariateSpline :
+        a bivariate spline over a rectangular mesh on a sphere
+    SmoothSphereBivariateSpline :
+        a smoothing bivariate spline in spherical coordinates
+    LSQSphereBivariateSpline :
+        a bivariate spline in spherical coordinates using weighted
+        least-squares fitting
+    RectBivariateSpline :
+        a bivariate spline over a rectangular mesh
+    bisplrep :
+        a function to find a bivariate B-spline representation of a surface
+    bisplev :
+        a function to evaluate a bivariate B-spline and its derivatives
+
+    Notes
+    -----
+    The length of `x`, `y` and `z` should be at least ``(kx+1) * (ky+1)``.
+
+    If the input data is such that input dimensions have incommensurate
+    units and differ by many orders of magnitude, the interpolant may have
+    numerical artifacts. Consider rescaling the data before interpolating.
+
+    This routine constructs spline knot vectors automatically via the FITPACK
+    algorithm. The spline knots may be placed away from the data points. For
+    some data sets, this routine may fail to construct an interpolating spline,
+    even if one is requested via ``s=0`` parameter. In such situations, it is
+    recommended to use `bisplrep` / `bisplev` directly instead of this routine
+    and, if needed, increase the values of ``nxest`` and ``nyest`` parameters
+    of `bisplrep`.
+
+    For linear interpolation, prefer `LinearNDInterpolator`.
+    See ``https://gist.github.com/ev-br/8544371b40f414b7eaf3fe6217209bff``
+    for discussion.
+
+    """
+
+    def __init__(self, x, y, z, w=None, bbox=[None] * 4, kx=3, ky=3, s=None,
+                 eps=1e-16):
+
+        x, y, z, w = self._validate_input(x, y, z, w, kx, ky, eps)
+        bbox = ravel(bbox)
+        if not bbox.shape == (4,):
+            raise ValueError('bbox shape should be (4,)')
+        if s is not None and not s >= 0.0:
+            raise ValueError("s should be s >= 0.0")
+
+        xb, xe, yb, ye = bbox
+        nx, tx, ny, ty, c, fp, wrk1, ier = dfitpack.surfit_smth(x, y, z, w,
+                                                                xb, xe, yb,
+                                                                ye, kx, ky,
+                                                                s=s, eps=eps,
+                                                                lwrk2=1)
+        if ier > 10:          # lwrk2 was to small, re-run
+            nx, tx, ny, ty, c, fp, wrk1, ier = dfitpack.surfit_smth(x, y, z, w,
+                                                                    xb, xe, yb,
+                                                                    ye, kx, ky,
+                                                                    s=s,
+                                                                    eps=eps,
+                                                                    lwrk2=ier)
+        if ier in [0, -1, -2]:  # normal return
+            pass
+        else:
+            message = _surfit_messages.get(ier, 'ier=%s' % (ier))
+            warnings.warn(message, stacklevel=2)
+
+        self.fp = fp
+        self.tck = tx[:nx], ty[:ny], c[:(nx-kx-1)*(ny-ky-1)]
+        self.degrees = kx, ky
+
+
+class LSQBivariateSpline(BivariateSpline):
+    """
+    Weighted least-squares bivariate spline approximation.
+
+    Parameters
+    ----------
+    x, y, z : array_like
+        1-D sequences of data points (order is not important).
+    tx, ty : array_like
+        Strictly ordered 1-D sequences of knots coordinates.
+    w : array_like, optional
+        Positive 1-D array of weights, of the same length as `x`, `y` and `z`.
+    bbox : (4,) array_like, optional
+        Sequence of length 4 specifying the boundary of the rectangular
+        approximation domain.  By default,
+        ``bbox=[min(x,tx),max(x,tx), min(y,ty),max(y,ty)]``.
+    kx, ky : ints, optional
+        Degrees of the bivariate spline. Default is 3.
+    eps : float, optional
+        A threshold for determining the effective rank of an over-determined
+        linear system of equations. `eps` should have a value within the open
+        interval ``(0, 1)``, the default is 1e-16.
+
+    See Also
+    --------
+    BivariateSpline :
+        a base class for bivariate splines.
+    UnivariateSpline :
+        a smooth univariate spline to fit a given set of data points.
+    SmoothBivariateSpline :
+        a smoothing bivariate spline through the given points
+    RectSphereBivariateSpline :
+        a bivariate spline over a rectangular mesh on a sphere
+    SmoothSphereBivariateSpline :
+        a smoothing bivariate spline in spherical coordinates
+    LSQSphereBivariateSpline :
+        a bivariate spline in spherical coordinates using weighted
+        least-squares fitting
+    RectBivariateSpline :
+        a bivariate spline over a rectangular mesh.
+    bisplrep :
+        a function to find a bivariate B-spline representation of a surface
+    bisplev :
+        a function to evaluate a bivariate B-spline and its derivatives
+
+    Notes
+    -----
+    The length of `x`, `y` and `z` should be at least ``(kx+1) * (ky+1)``.
+
+    If the input data is such that input dimensions have incommensurate
+    units and differ by many orders of magnitude, the interpolant may have
+    numerical artifacts. Consider rescaling the data before interpolating.
+
+    """
+
+    def __init__(self, x, y, z, tx, ty, w=None, bbox=[None]*4, kx=3, ky=3,
+                 eps=None):
+
+        x, y, z, w = self._validate_input(x, y, z, w, kx, ky, eps)
+        bbox = ravel(bbox)
+        if not bbox.shape == (4,):
+            raise ValueError('bbox shape should be (4,)')
+
+        nx = 2*kx+2+len(tx)
+        ny = 2*ky+2+len(ty)
+        # The Fortran subroutine "surfit" (called as dfitpack.surfit_lsq)
+        # requires that the knot arrays passed as input should be "real
+        # array(s) of dimension nmax" where "nmax" refers to the greater of nx
+        # and ny. We pad the tx1/ty1 arrays here so that this is satisfied, and
+        # slice them to the desired sizes upon return.
+        nmax = max(nx, ny)
+        tx1 = zeros((nmax,), float)
+        ty1 = zeros((nmax,), float)
+        tx1[kx+1:nx-kx-1] = tx
+        ty1[ky+1:ny-ky-1] = ty
+
+        xb, xe, yb, ye = bbox
+        tx1, ty1, c, fp, ier = dfitpack.surfit_lsq(x, y, z, nx, tx1, ny, ty1,
+                                                   w, xb, xe, yb, ye,
+                                                   kx, ky, eps, lwrk2=1)
+        if ier > 10:
+            tx1, ty1, c, fp, ier = dfitpack.surfit_lsq(x, y, z,
+                                                       nx, tx1, ny, ty1, w,
+                                                       xb, xe, yb, ye,
+                                                       kx, ky, eps, lwrk2=ier)
+        if ier in [0, -1, -2]:  # normal return
+            pass
+        else:
+            if ier < -2:
+                deficiency = (nx-kx-1)*(ny-ky-1)+ier
+                message = _surfit_messages.get(-3) % (deficiency)
+            else:
+                message = _surfit_messages.get(ier, 'ier=%s' % (ier))
+            warnings.warn(message, stacklevel=2)
+        self.fp = fp
+        self.tck = tx1[:nx], ty1[:ny], c
+        self.degrees = kx, ky
+
+
+class RectBivariateSpline(BivariateSpline):
+    """
+    Bivariate spline approximation over a rectangular mesh.
+
+    Can be used for both smoothing and interpolating data.
+
+    Parameters
+    ----------
+    x,y : array_like
+        1-D arrays of coordinates in strictly ascending order.
+        Evaluated points outside the data range will be extrapolated.
+    z : array_like
+        2-D array of data with shape (x.size,y.size).
+    bbox : array_like, optional
+        Sequence of length 4 specifying the boundary of the rectangular
+        approximation domain, which means the start and end spline knots of
+        each dimension are set by these values. By default,
+        ``bbox=[min(x), max(x), min(y), max(y)]``.
+    kx, ky : ints, optional
+        Degrees of the bivariate spline. Default is 3.
+    s : float, optional
+        Positive smoothing factor defined for estimation condition:
+        ``sum((z[i]-f(x[i], y[i]))**2, axis=0) <= s`` where f is a spline
+        function. Default is ``s=0``, which is for interpolation.
+
+    See Also
+    --------
+    BivariateSpline :
+        a base class for bivariate splines.
+    UnivariateSpline :
+        a smooth univariate spline to fit a given set of data points.
+    SmoothBivariateSpline :
+        a smoothing bivariate spline through the given points
+    LSQBivariateSpline :
+        a bivariate spline using weighted least-squares fitting
+    RectSphereBivariateSpline :
+        a bivariate spline over a rectangular mesh on a sphere
+    SmoothSphereBivariateSpline :
+        a smoothing bivariate spline in spherical coordinates
+    LSQSphereBivariateSpline :
+        a bivariate spline in spherical coordinates using weighted
+        least-squares fitting
+    bisplrep :
+        a function to find a bivariate B-spline representation of a surface
+    bisplev :
+        a function to evaluate a bivariate B-spline and its derivatives
+
+    Notes
+    -----
+
+    If the input data is such that input dimensions have incommensurate
+    units and differ by many orders of magnitude, the interpolant may have
+    numerical artifacts. Consider rescaling the data before interpolating.
+
+    """
+
+    def __init__(self, x, y, z, bbox=[None] * 4, kx=3, ky=3, s=0):
+        x, y, bbox = ravel(x), ravel(y), ravel(bbox)
+        z = np.asarray(z)
+        if not np.all(diff(x) > 0.0):
+            raise ValueError('x must be strictly increasing')
+        if not np.all(diff(y) > 0.0):
+            raise ValueError('y must be strictly increasing')
+        if not x.size == z.shape[0]:
+            raise ValueError('x dimension of z must have same number of '
+                             'elements as x')
+        if not y.size == z.shape[1]:
+            raise ValueError('y dimension of z must have same number of '
+                             'elements as y')
+        if not bbox.shape == (4,):
+            raise ValueError('bbox shape should be (4,)')
+        if s is not None and not s >= 0.0:
+            raise ValueError("s should be s >= 0.0")
+
+        z = ravel(z)
+        xb, xe, yb, ye = bbox
+        nx, tx, ny, ty, c, fp, ier = dfitpack.regrid_smth(x, y, z, xb, xe, yb,
+                                                          ye, kx, ky, s)
+
+        if ier not in [0, -1, -2]:
+            msg = _surfit_messages.get(ier, 'ier=%s' % (ier))
+            raise ValueError(msg)
+
+        self.fp = fp
+        self.tck = tx[:nx], ty[:ny], c[:(nx - kx - 1) * (ny - ky - 1)]
+        self.degrees = kx, ky
+
+
+_spherefit_messages = _surfit_messages.copy()
+_spherefit_messages[10] = """
+ERROR. On entry, the input data are controlled on validity. The following
+       restrictions must be satisfied:
+            -1<=iopt<=1,  m>=2, ntest>=8 ,npest >=8, 0<eps<1,
+            0<=teta(i)<=pi, 0<=phi(i)<=2*pi, w(i)>0, i=1,...,m
+            lwrk1 >= 185+52*v+10*u+14*u*v+8*(u-1)*v**2+8*m
+            kwrk >= m+(ntest-7)*(npest-7)
+            if iopt=-1: 8<=nt<=ntest , 9<=np<=npest
+                        0<tt(5)<tt(6)<...<tt(nt-4)<pi
+                        0<tp(5)<tp(6)<...<tp(np-4)<2*pi
+            if iopt>=0: s>=0
+            if one of these conditions is found to be violated,control
+            is immediately repassed to the calling program. in that
+            case there is no approximation returned."""
+_spherefit_messages[-3] = """
+WARNING. The coefficients of the spline returned have been computed as the
+         minimal norm least-squares solution of a (numerically) rank
+         deficient system (deficiency=%i, rank=%i). Especially if the rank
+         deficiency, which is computed by 6+(nt-8)*(np-7)+ier, is large,
+         the results may be inaccurate. They could also seriously depend on
+         the value of eps."""
+
+
+class SphereBivariateSpline(_BivariateSplineBase):
+    """
+    Bivariate spline s(x,y) of degrees 3 on a sphere, calculated from a
+    given set of data points (theta,phi,r).
+
+    .. versionadded:: 0.11.0
+
+    See Also
+    --------
+    bisplrep :
+        a function to find a bivariate B-spline representation of a surface
+    bisplev :
+        a function to evaluate a bivariate B-spline and its derivatives
+    UnivariateSpline :
+        a smooth univariate spline to fit a given set of data points.
+    SmoothBivariateSpline :
+        a smoothing bivariate spline through the given points
+    LSQUnivariateSpline :
+        a univariate spline using weighted least-squares fitting
+    """
+
+    def __call__(self, theta, phi, dtheta=0, dphi=0, grid=True):
+        """
+        Evaluate the spline or its derivatives at given positions.
+
+        Parameters
+        ----------
+        theta, phi : array_like
+            Input coordinates.
+
+            If `grid` is False, evaluate the spline at points
+            ``(theta[i], phi[i]), i=0, ..., len(x)-1``.  Standard
+            Numpy broadcasting is obeyed.
+
+            If `grid` is True: evaluate spline at the grid points
+            defined by the coordinate arrays theta, phi. The arrays
+            must be sorted to increasing order.
+            The ordering of axes is consistent with
+            ``np.meshgrid(..., indexing="ij")`` and inconsistent with the
+            default ordering ``np.meshgrid(..., indexing="xy")``.
+        dtheta : int, optional
+            Order of theta-derivative
+
+            .. versionadded:: 0.14.0
+        dphi : int
+            Order of phi-derivative
+
+            .. versionadded:: 0.14.0
+        grid : bool
+            Whether to evaluate the results on a grid spanned by the
+            input arrays, or at points specified by the input arrays.
+
+            .. versionadded:: 0.14.0
+
+        Examples
+        --------
+
+        Suppose that we want to use splines to interpolate a bivariate function on a
+        sphere. The value of the function is known on a grid of longitudes and
+        colatitudes.
+
+        >>> import numpy as np
+        >>> from scipy.interpolate import RectSphereBivariateSpline
+        >>> def f(theta, phi):
+        ...     return np.sin(theta) * np.cos(phi)
+
+        We evaluate the function on the grid. Note that the default indexing="xy"
+        of meshgrid would result in an unexpected (transposed) result after
+        interpolation.
+
+        >>> thetaarr = np.linspace(0, np.pi, 22)[1:-1]
+        >>> phiarr = np.linspace(0, 2 * np.pi, 21)[:-1]
+        >>> thetagrid, phigrid = np.meshgrid(thetaarr, phiarr, indexing="ij")
+        >>> zdata = f(thetagrid, phigrid)
+
+        We next set up the interpolator and use it to evaluate the function
+        on a finer grid.
+
+        >>> rsbs = RectSphereBivariateSpline(thetaarr, phiarr, zdata)
+        >>> thetaarr_fine = np.linspace(0, np.pi, 200)
+        >>> phiarr_fine = np.linspace(0, 2 * np.pi, 200)
+        >>> zdata_fine = rsbs(thetaarr_fine, phiarr_fine)
+
+        Finally we plot the coarsly-sampled input data alongside the
+        finely-sampled interpolated data to check that they agree.
+
+        >>> import matplotlib.pyplot as plt
+        >>> fig = plt.figure()
+        >>> ax1 = fig.add_subplot(1, 2, 1)
+        >>> ax2 = fig.add_subplot(1, 2, 2)
+        >>> ax1.imshow(zdata)
+        >>> ax2.imshow(zdata_fine)
+        >>> plt.show()
+        """
+        theta = np.asarray(theta)
+        phi = np.asarray(phi)
+
+        if theta.size > 0 and (theta.min() < 0. or theta.max() > np.pi):
+            raise ValueError("requested theta out of bounds.")
+
+        return _BivariateSplineBase.__call__(self, theta, phi,
+                                             dx=dtheta, dy=dphi, grid=grid)
+
+    def ev(self, theta, phi, dtheta=0, dphi=0):
+        """
+        Evaluate the spline at points
+
+        Returns the interpolated value at ``(theta[i], phi[i]),
+        i=0,...,len(theta)-1``.
+
+        Parameters
+        ----------
+        theta, phi : array_like
+            Input coordinates. Standard Numpy broadcasting is obeyed.
+            The ordering of axes is consistent with
+            np.meshgrid(..., indexing="ij") and inconsistent with the
+            default ordering np.meshgrid(..., indexing="xy").
+        dtheta : int, optional
+            Order of theta-derivative
+
+            .. versionadded:: 0.14.0
+        dphi : int, optional
+            Order of phi-derivative
+
+            .. versionadded:: 0.14.0
+
+        Examples
+        --------
+        Suppose that we want to use splines to interpolate a bivariate function on a
+        sphere. The value of the function is known on a grid of longitudes and
+        colatitudes.
+
+        >>> import numpy as np
+        >>> from scipy.interpolate import RectSphereBivariateSpline
+        >>> def f(theta, phi):
+        ...     return np.sin(theta) * np.cos(phi)
+
+        We evaluate the function on the grid. Note that the default indexing="xy"
+        of meshgrid would result in an unexpected (transposed) result after
+        interpolation.
+
+        >>> thetaarr = np.linspace(0, np.pi, 22)[1:-1]
+        >>> phiarr = np.linspace(0, 2 * np.pi, 21)[:-1]
+        >>> thetagrid, phigrid = np.meshgrid(thetaarr, phiarr, indexing="ij")
+        >>> zdata = f(thetagrid, phigrid)
+
+        We next set up the interpolator and use it to evaluate the function
+        at points not on the original grid.
+
+        >>> rsbs = RectSphereBivariateSpline(thetaarr, phiarr, zdata)
+        >>> thetainterp = np.linspace(thetaarr[0], thetaarr[-1], 200)
+        >>> phiinterp = np.linspace(phiarr[0], phiarr[-1], 200)
+        >>> zinterp = rsbs.ev(thetainterp, phiinterp)
+
+        Finally we plot the original data for a diagonal slice through the
+        initial grid, and the spline approximation along the same slice.
+
+        >>> import matplotlib.pyplot as plt
+        >>> fig = plt.figure()
+        >>> ax1 = fig.add_subplot(1, 1, 1)
+        >>> ax1.plot(np.sin(thetaarr) * np.sin(phiarr), np.diag(zdata), "or")
+        >>> ax1.plot(np.sin(thetainterp) * np.sin(phiinterp), zinterp, "-b")
+        >>> plt.show()
+        """
+        return self.__call__(theta, phi, dtheta=dtheta, dphi=dphi, grid=False)
+
+
+class SmoothSphereBivariateSpline(SphereBivariateSpline):
+    """
+    Smooth bivariate spline approximation in spherical coordinates.
+
+    .. versionadded:: 0.11.0
+
+    Parameters
+    ----------
+    theta, phi, r : array_like
+        1-D sequences of data points (order is not important). Coordinates
+        must be given in radians. Theta must lie within the interval
+        ``[0, pi]``, and phi must lie within the interval ``[0, 2pi]``.
+    w : array_like, optional
+        Positive 1-D sequence of weights.
+    s : float, optional
+        Positive smoothing factor defined for estimation condition:
+        ``sum((w(i)*(r(i) - s(theta(i), phi(i))))**2, axis=0) <= s``
+        Default ``s=len(w)`` which should be a good value if ``1/w[i]`` is an
+        estimate of the standard deviation of ``r[i]``.
+    eps : float, optional
+        A threshold for determining the effective rank of an over-determined
+        linear system of equations. `eps` should have a value within the open
+        interval ``(0, 1)``, the default is 1e-16.
+
+    See Also
+    --------
+    BivariateSpline :
+        a base class for bivariate splines.
+    UnivariateSpline :
+        a smooth univariate spline to fit a given set of data points.
+    SmoothBivariateSpline :
+        a smoothing bivariate spline through the given points
+    LSQBivariateSpline :
+        a bivariate spline using weighted least-squares fitting
+    RectSphereBivariateSpline :
+        a bivariate spline over a rectangular mesh on a sphere
+    LSQSphereBivariateSpline :
+        a bivariate spline in spherical coordinates using weighted
+        least-squares fitting
+    RectBivariateSpline :
+        a bivariate spline over a rectangular mesh.
+    bisplrep :
+        a function to find a bivariate B-spline representation of a surface
+    bisplev :
+        a function to evaluate a bivariate B-spline and its derivatives
+
+    Notes
+    -----
+    For more information, see the FITPACK_ site about this function.
+
+    .. _FITPACK: http://www.netlib.org/dierckx/sphere.f
+
+    Examples
+    --------
+    Suppose we have global data on a coarse grid (the input data does not
+    have to be on a grid):
+
+    >>> import numpy as np
+    >>> theta = np.linspace(0., np.pi, 7)
+    >>> phi = np.linspace(0., 2*np.pi, 9)
+    >>> data = np.empty((theta.shape[0], phi.shape[0]))
+    >>> data[:,0], data[0,:], data[-1,:] = 0., 0., 0.
+    >>> data[1:-1,1], data[1:-1,-1] = 1., 1.
+    >>> data[1,1:-1], data[-2,1:-1] = 1., 1.
+    >>> data[2:-2,2], data[2:-2,-2] = 2., 2.
+    >>> data[2,2:-2], data[-3,2:-2] = 2., 2.
+    >>> data[3,3:-2] = 3.
+    >>> data = np.roll(data, 4, 1)
+
+    We need to set up the interpolator object
+
+    >>> lats, lons = np.meshgrid(theta, phi)
+    >>> from scipy.interpolate import SmoothSphereBivariateSpline
+    >>> lut = SmoothSphereBivariateSpline(lats.ravel(), lons.ravel(),
+    ...                                   data.T.ravel(), s=3.5)
+
+    As a first test, we'll see what the algorithm returns when run on the
+    input coordinates
+
+    >>> data_orig = lut(theta, phi)
+
+    Finally we interpolate the data to a finer grid
+
+    >>> fine_lats = np.linspace(0., np.pi, 70)
+    >>> fine_lons = np.linspace(0., 2 * np.pi, 90)
+
+    >>> data_smth = lut(fine_lats, fine_lons)
+
+    >>> import matplotlib.pyplot as plt
+    >>> fig = plt.figure()
+    >>> ax1 = fig.add_subplot(131)
+    >>> ax1.imshow(data, interpolation='nearest')
+    >>> ax2 = fig.add_subplot(132)
+    >>> ax2.imshow(data_orig, interpolation='nearest')
+    >>> ax3 = fig.add_subplot(133)
+    >>> ax3.imshow(data_smth, interpolation='nearest')
+    >>> plt.show()
+
+    """
+
+    def __init__(self, theta, phi, r, w=None, s=0., eps=1E-16):
+
+        theta, phi, r = np.asarray(theta), np.asarray(phi), np.asarray(r)
+
+        # input validation
+        if not ((0.0 <= theta).all() and (theta <= np.pi).all()):
+            raise ValueError('theta should be between [0, pi]')
+        if not ((0.0 <= phi).all() and (phi <= 2.0 * np.pi).all()):
+            raise ValueError('phi should be between [0, 2pi]')
+        if w is not None:
+            w = np.asarray(w)
+            if not (w >= 0.0).all():
+                raise ValueError('w should be positive')
+        if not s >= 0.0:
+            raise ValueError('s should be positive')
+        if not 0.0 < eps < 1.0:
+            raise ValueError('eps should be between (0, 1)')
+
+        nt_, tt_, np_, tp_, c, fp, ier = dfitpack.spherfit_smth(theta, phi,
+                                                                r, w=w, s=s,
+                                                                eps=eps)
+        if ier not in [0, -1, -2]:
+            message = _spherefit_messages.get(ier, 'ier=%s' % (ier))
+            raise ValueError(message)
+
+        self.fp = fp
+        self.tck = tt_[:nt_], tp_[:np_], c[:(nt_ - 4) * (np_ - 4)]
+        self.degrees = (3, 3)
+
+    def __call__(self, theta, phi, dtheta=0, dphi=0, grid=True):
+
+        theta = np.asarray(theta)
+        phi = np.asarray(phi)
+
+        if phi.size > 0 and (phi.min() < 0. or phi.max() > 2. * np.pi):
+            raise ValueError("requested phi out of bounds.")
+
+        return SphereBivariateSpline.__call__(self, theta, phi, dtheta=dtheta,
+                                              dphi=dphi, grid=grid)
+
+
+class LSQSphereBivariateSpline(SphereBivariateSpline):
+    """
+    Weighted least-squares bivariate spline approximation in spherical
+    coordinates.
+
+    Determines a smoothing bicubic spline according to a given
+    set of knots in the `theta` and `phi` directions.
+
+    .. versionadded:: 0.11.0
+
+    Parameters
+    ----------
+    theta, phi, r : array_like
+        1-D sequences of data points (order is not important). Coordinates
+        must be given in radians. Theta must lie within the interval
+        ``[0, pi]``, and phi must lie within the interval ``[0, 2pi]``.
+    tt, tp : array_like
+        Strictly ordered 1-D sequences of knots coordinates.
+        Coordinates must satisfy ``0 < tt[i] < pi``, ``0 < tp[i] < 2*pi``.
+    w : array_like, optional
+        Positive 1-D sequence of weights, of the same length as `theta`, `phi`
+        and `r`.
+    eps : float, optional
+        A threshold for determining the effective rank of an over-determined
+        linear system of equations. `eps` should have a value within the
+        open interval ``(0, 1)``, the default is 1e-16.
+
+    See Also
+    --------
+    BivariateSpline :
+        a base class for bivariate splines.
+    UnivariateSpline :
+        a smooth univariate spline to fit a given set of data points.
+    SmoothBivariateSpline :
+        a smoothing bivariate spline through the given points
+    LSQBivariateSpline :
+        a bivariate spline using weighted least-squares fitting
+    RectSphereBivariateSpline :
+        a bivariate spline over a rectangular mesh on a sphere
+    SmoothSphereBivariateSpline :
+        a smoothing bivariate spline in spherical coordinates
+    RectBivariateSpline :
+        a bivariate spline over a rectangular mesh.
+    bisplrep :
+        a function to find a bivariate B-spline representation of a surface
+    bisplev :
+        a function to evaluate a bivariate B-spline and its derivatives
+
+    Notes
+    -----
+    For more information, see the FITPACK_ site about this function.
+
+    .. _FITPACK: http://www.netlib.org/dierckx/sphere.f
+
+    Examples
+    --------
+    Suppose we have global data on a coarse grid (the input data does not
+    have to be on a grid):
+
+    >>> from scipy.interpolate import LSQSphereBivariateSpline
+    >>> import numpy as np
+    >>> import matplotlib.pyplot as plt
+
+    >>> theta = np.linspace(0, np.pi, num=7)
+    >>> phi = np.linspace(0, 2*np.pi, num=9)
+    >>> data = np.empty((theta.shape[0], phi.shape[0]))
+    >>> data[:,0], data[0,:], data[-1,:] = 0., 0., 0.
+    >>> data[1:-1,1], data[1:-1,-1] = 1., 1.
+    >>> data[1,1:-1], data[-2,1:-1] = 1., 1.
+    >>> data[2:-2,2], data[2:-2,-2] = 2., 2.
+    >>> data[2,2:-2], data[-3,2:-2] = 2., 2.
+    >>> data[3,3:-2] = 3.
+    >>> data = np.roll(data, 4, 1)
+
+    We need to set up the interpolator object. Here, we must also specify the
+    coordinates of the knots to use.
+
+    >>> lats, lons = np.meshgrid(theta, phi)
+    >>> knotst, knotsp = theta.copy(), phi.copy()
+    >>> knotst[0] += .0001
+    >>> knotst[-1] -= .0001
+    >>> knotsp[0] += .0001
+    >>> knotsp[-1] -= .0001
+    >>> lut = LSQSphereBivariateSpline(lats.ravel(), lons.ravel(),
+    ...                                data.T.ravel(), knotst, knotsp)
+
+    As a first test, we'll see what the algorithm returns when run on the
+    input coordinates
+
+    >>> data_orig = lut(theta, phi)
+
+    Finally we interpolate the data to a finer grid
+
+    >>> fine_lats = np.linspace(0., np.pi, 70)
+    >>> fine_lons = np.linspace(0., 2*np.pi, 90)
+    >>> data_lsq = lut(fine_lats, fine_lons)
+
+    >>> fig = plt.figure()
+    >>> ax1 = fig.add_subplot(131)
+    >>> ax1.imshow(data, interpolation='nearest')
+    >>> ax2 = fig.add_subplot(132)
+    >>> ax2.imshow(data_orig, interpolation='nearest')
+    >>> ax3 = fig.add_subplot(133)
+    >>> ax3.imshow(data_lsq, interpolation='nearest')
+    >>> plt.show()
+
+    """
+
+    def __init__(self, theta, phi, r, tt, tp, w=None, eps=1E-16):
+
+        theta, phi, r = np.asarray(theta), np.asarray(phi), np.asarray(r)
+        tt, tp = np.asarray(tt), np.asarray(tp)
+
+        if not ((0.0 <= theta).all() and (theta <= np.pi).all()):
+            raise ValueError('theta should be between [0, pi]')
+        if not ((0.0 <= phi).all() and (phi <= 2*np.pi).all()):
+            raise ValueError('phi should be between [0, 2pi]')
+        if not ((0.0 < tt).all() and (tt < np.pi).all()):
+            raise ValueError('tt should be between (0, pi)')
+        if not ((0.0 < tp).all() and (tp < 2*np.pi).all()):
+            raise ValueError('tp should be between (0, 2pi)')
+        if w is not None:
+            w = np.asarray(w)
+            if not (w >= 0.0).all():
+                raise ValueError('w should be positive')
+        if not 0.0 < eps < 1.0:
+            raise ValueError('eps should be between (0, 1)')
+
+        nt_, np_ = 8 + len(tt), 8 + len(tp)
+        tt_, tp_ = zeros((nt_,), float), zeros((np_,), float)
+        tt_[4:-4], tp_[4:-4] = tt, tp
+        tt_[-4:], tp_[-4:] = np.pi, 2. * np.pi
+        tt_, tp_, c, fp, ier = dfitpack.spherfit_lsq(theta, phi, r, tt_, tp_,
+                                                     w=w, eps=eps)
+        if ier > 0:
+            message = _spherefit_messages.get(ier, 'ier=%s' % (ier))
+            raise ValueError(message)
+
+        self.fp = fp
+        self.tck = tt_, tp_, c
+        self.degrees = (3, 3)
+
+    def __call__(self, theta, phi, dtheta=0, dphi=0, grid=True):
+
+        theta = np.asarray(theta)
+        phi = np.asarray(phi)
+
+        if phi.size > 0 and (phi.min() < 0. or phi.max() > 2. * np.pi):
+            raise ValueError("requested phi out of bounds.")
+
+        return SphereBivariateSpline.__call__(self, theta, phi, dtheta=dtheta,
+                                              dphi=dphi, grid=grid)
+
+
+_spfit_messages = _surfit_messages.copy()
+_spfit_messages[10] = """
+ERROR: on entry, the input data are controlled on validity
+       the following restrictions must be satisfied.
+          -1<=iopt(1)<=1, 0<=iopt(2)<=1, 0<=iopt(3)<=1,
+          -1<=ider(1)<=1, 0<=ider(2)<=1, ider(2)=0 if iopt(2)=0.
+          -1<=ider(3)<=1, 0<=ider(4)<=1, ider(4)=0 if iopt(3)=0.
+          mu >= mumin (see above), mv >= 4, nuest >=8, nvest >= 8,
+          kwrk>=5+mu+mv+nuest+nvest,
+          lwrk >= 12+nuest*(mv+nvest+3)+nvest*24+4*mu+8*mv+max(nuest,mv+nvest)
+          0< u(i-1)<u(i)< pi,i=2,..,mu,
+          -pi<=v(1)< pi, v(1)<v(i-1)<v(i)<v(1)+2*pi, i=3,...,mv
+          if iopt(1)=-1: 8<=nu<=min(nuest,mu+6+iopt(2)+iopt(3))
+                         0<tu(5)<tu(6)<...<tu(nu-4)< pi
+                         8<=nv<=min(nvest,mv+7)
+                         v(1)<tv(5)<tv(6)<...<tv(nv-4)<v(1)+2*pi
+                         the schoenberg-whitney conditions, i.e. there must be
+                         subset of grid coordinates uu(p) and vv(q) such that
+                            tu(p) < uu(p) < tu(p+4) ,p=1,...,nu-4
+                            (iopt(2)=1 and iopt(3)=1 also count for a uu-value
+                            tv(q) < vv(q) < tv(q+4) ,q=1,...,nv-4
+                            (vv(q) is either a value v(j) or v(j)+2*pi)
+          if iopt(1)>=0: s>=0
+          if s=0: nuest>=mu+6+iopt(2)+iopt(3), nvest>=mv+7
+       if one of these conditions is found to be violated,control is
+       immediately repassed to the calling program. in that case there is no
+       approximation returned."""
+
+
+class RectSphereBivariateSpline(SphereBivariateSpline):
+    """
+    Bivariate spline approximation over a rectangular mesh on a sphere.
+
+    Can be used for smoothing data.
+
+    .. versionadded:: 0.11.0
+
+    Parameters
+    ----------
+    u : array_like
+        1-D array of colatitude coordinates in strictly ascending order.
+        Coordinates must be given in radians and lie within the open interval
+        ``(0, pi)``.
+    v : array_like
+        1-D array of longitude coordinates in strictly ascending order.
+        Coordinates must be given in radians. First element (``v[0]``) must lie
+        within the interval ``[-pi, pi)``. Last element (``v[-1]``) must satisfy
+        ``v[-1] <= v[0] + 2*pi``.
+    r : array_like
+        2-D array of data with shape ``(u.size, v.size)``.
+    s : float, optional
+        Positive smoothing factor defined for estimation condition
+        (``s=0`` is for interpolation).
+    pole_continuity : bool or (bool, bool), optional
+        Order of continuity at the poles ``u=0`` (``pole_continuity[0]``) and
+        ``u=pi`` (``pole_continuity[1]``).  The order of continuity at the pole
+        will be 1 or 0 when this is True or False, respectively.
+        Defaults to False.
+    pole_values : float or (float, float), optional
+        Data values at the poles ``u=0`` and ``u=pi``.  Either the whole
+        parameter or each individual element can be None.  Defaults to None.
+    pole_exact : bool or (bool, bool), optional
+        Data value exactness at the poles ``u=0`` and ``u=pi``.  If True, the
+        value is considered to be the right function value, and it will be
+        fitted exactly. If False, the value will be considered to be a data
+        value just like the other data values.  Defaults to False.
+    pole_flat : bool or (bool, bool), optional
+        For the poles at ``u=0`` and ``u=pi``, specify whether or not the
+        approximation has vanishing derivatives.  Defaults to False.
+
+    See Also
+    --------
+    BivariateSpline :
+        a base class for bivariate splines.
+    UnivariateSpline :
+        a smooth univariate spline to fit a given set of data points.
+    SmoothBivariateSpline :
+        a smoothing bivariate spline through the given points
+    LSQBivariateSpline :
+        a bivariate spline using weighted least-squares fitting
+    SmoothSphereBivariateSpline :
+        a smoothing bivariate spline in spherical coordinates
+    LSQSphereBivariateSpline :
+        a bivariate spline in spherical coordinates using weighted
+        least-squares fitting
+    RectBivariateSpline :
+        a bivariate spline over a rectangular mesh.
+    bisplrep :
+        a function to find a bivariate B-spline representation of a surface
+    bisplev :
+        a function to evaluate a bivariate B-spline and its derivatives
+
+    Notes
+    -----
+    Currently, only the smoothing spline approximation (``iopt[0] = 0`` and
+    ``iopt[0] = 1`` in the FITPACK routine) is supported.  The exact
+    least-squares spline approximation is not implemented yet.
+
+    When actually performing the interpolation, the requested `v` values must
+    lie within the same length 2pi interval that the original `v` values were
+    chosen from.
+
+    For more information, see the FITPACK_ site about this function.
+
+    .. _FITPACK: http://www.netlib.org/dierckx/spgrid.f
+
+    Examples
+    --------
+    Suppose we have global data on a coarse grid
+
+    >>> import numpy as np
+    >>> lats = np.linspace(10, 170, 9) * np.pi / 180.
+    >>> lons = np.linspace(0, 350, 18) * np.pi / 180.
+    >>> data = np.dot(np.atleast_2d(90. - np.linspace(-80., 80., 18)).T,
+    ...               np.atleast_2d(180. - np.abs(np.linspace(0., 350., 9)))).T
+
+    We want to interpolate it to a global one-degree grid
+
+    >>> new_lats = np.linspace(1, 180, 180) * np.pi / 180
+    >>> new_lons = np.linspace(1, 360, 360) * np.pi / 180
+    >>> new_lats, new_lons = np.meshgrid(new_lats, new_lons)
+
+    We need to set up the interpolator object
+
+    >>> from scipy.interpolate import RectSphereBivariateSpline
+    >>> lut = RectSphereBivariateSpline(lats, lons, data)
+
+    Finally we interpolate the data.  The `RectSphereBivariateSpline` object
+    only takes 1-D arrays as input, therefore we need to do some reshaping.
+
+    >>> data_interp = lut.ev(new_lats.ravel(),
+    ...                      new_lons.ravel()).reshape((360, 180)).T
+
+    Looking at the original and the interpolated data, one can see that the
+    interpolant reproduces the original data very well:
+
+    >>> import matplotlib.pyplot as plt
+    >>> fig = plt.figure()
+    >>> ax1 = fig.add_subplot(211)
+    >>> ax1.imshow(data, interpolation='nearest')
+    >>> ax2 = fig.add_subplot(212)
+    >>> ax2.imshow(data_interp, interpolation='nearest')
+    >>> plt.show()
+
+    Choosing the optimal value of ``s`` can be a delicate task. Recommended
+    values for ``s`` depend on the accuracy of the data values.  If the user
+    has an idea of the statistical errors on the data, she can also find a
+    proper estimate for ``s``. By assuming that, if she specifies the
+    right ``s``, the interpolator will use a spline ``f(u,v)`` which exactly
+    reproduces the function underlying the data, she can evaluate
+    ``sum((r(i,j)-s(u(i),v(j)))**2)`` to find a good estimate for this ``s``.
+    For example, if she knows that the statistical errors on her
+    ``r(i,j)``-values are not greater than 0.1, she may expect that a good
+    ``s`` should have a value not larger than ``u.size * v.size * (0.1)**2``.
+
+    If nothing is known about the statistical error in ``r(i,j)``, ``s`` must
+    be determined by trial and error.  The best is then to start with a very
+    large value of ``s`` (to determine the least-squares polynomial and the
+    corresponding upper bound ``fp0`` for ``s``) and then to progressively
+    decrease the value of ``s`` (say by a factor 10 in the beginning, i.e.
+    ``s = fp0 / 10, fp0 / 100, ...``  and more carefully as the approximation
+    shows more detail) to obtain closer fits.
+
+    The interpolation results for different values of ``s`` give some insight
+    into this process:
+
+    >>> fig2 = plt.figure()
+    >>> s = [3e9, 2e9, 1e9, 1e8]
+    >>> for idx, sval in enumerate(s, 1):
+    ...     lut = RectSphereBivariateSpline(lats, lons, data, s=sval)
+    ...     data_interp = lut.ev(new_lats.ravel(),
+    ...                          new_lons.ravel()).reshape((360, 180)).T
+    ...     ax = fig2.add_subplot(2, 2, idx)
+    ...     ax.imshow(data_interp, interpolation='nearest')
+    ...     ax.set_title(f"s = {sval:g}")
+    >>> plt.show()
+
+    """
+
+    def __init__(self, u, v, r, s=0., pole_continuity=False, pole_values=None,
+                 pole_exact=False, pole_flat=False):
+        iopt = np.array([0, 0, 0], dtype=dfitpack_int)
+        ider = np.array([-1, 0, -1, 0], dtype=dfitpack_int)
+        if pole_values is None:
+            pole_values = (None, None)
+        elif isinstance(pole_values, (float, np.float32, np.float64)):
+            pole_values = (pole_values, pole_values)
+        if isinstance(pole_continuity, bool):
+            pole_continuity = (pole_continuity, pole_continuity)
+        if isinstance(pole_exact, bool):
+            pole_exact = (pole_exact, pole_exact)
+        if isinstance(pole_flat, bool):
+            pole_flat = (pole_flat, pole_flat)
+
+        r0, r1 = pole_values
+        iopt[1:] = pole_continuity
+        if r0 is None:
+            ider[0] = -1
+        else:
+            ider[0] = pole_exact[0]
+
+        if r1 is None:
+            ider[2] = -1
+        else:
+            ider[2] = pole_exact[1]
+
+        ider[1], ider[3] = pole_flat
+
+        u, v = np.ravel(u), np.ravel(v)
+        r = np.asarray(r)
+
+        if not (0.0 < u[0] and u[-1] < np.pi):
+            raise ValueError('u should be between (0, pi)')
+        if not -np.pi <= v[0] < np.pi:
+            raise ValueError('v[0] should be between [-pi, pi)')
+        if not v[-1] <= v[0] + 2*np.pi:
+            raise ValueError('v[-1] should be v[0] + 2pi or less ')
+
+        if not np.all(np.diff(u) > 0.0):
+            raise ValueError('u must be strictly increasing')
+        if not np.all(np.diff(v) > 0.0):
+            raise ValueError('v must be strictly increasing')
+
+        if not u.size == r.shape[0]:
+            raise ValueError('u dimension of r must have same number of '
+                             'elements as u')
+        if not v.size == r.shape[1]:
+            raise ValueError('v dimension of r must have same number of '
+                             'elements as v')
+
+        if pole_continuity[1] is False and pole_flat[1] is True:
+            raise ValueError('if pole_continuity is False, so must be '
+                             'pole_flat')
+        if pole_continuity[0] is False and pole_flat[0] is True:
+            raise ValueError('if pole_continuity is False, so must be '
+                             'pole_flat')
+
+        if not s >= 0.0:
+            raise ValueError('s should be positive')
+
+        r = np.ravel(r)
+        nu, tu, nv, tv, c, fp, ier = dfitpack.regrid_smth_spher(iopt, ider,
+                                                                u.copy(),
+                                                                v.copy(),
+                                                                r.copy(),
+                                                                r0, r1, s)
+
+        if ier not in [0, -1, -2]:
+            msg = _spfit_messages.get(ier, 'ier=%s' % (ier))
+            raise ValueError(msg)
+
+        self.fp = fp
+        self.tck = tu[:nu], tv[:nv], c[:(nu - 4) * (nv-4)]
+        self.degrees = (3, 3)
+        self.v0 = v[0]
+
+    def __call__(self, theta, phi, dtheta=0, dphi=0, grid=True):
+
+        theta = np.asarray(theta)
+        phi = np.asarray(phi)
+
+        return SphereBivariateSpline.__call__(self, theta, phi, dtheta=dtheta,
+                                              dphi=dphi, grid=grid)

venv/lib/python3.10/site-packages/scipy/interpolate/_fitpack_impl.py

@@ -0,0 +1,805 @@
+"""
+fitpack (dierckx in netlib) --- A Python-C wrapper to FITPACK (by P. Dierckx).
+        FITPACK is a collection of FORTRAN programs for curve and surface
+        fitting with splines and tensor product splines.
+
+See
+ https://web.archive.org/web/20010524124604/http://www.cs.kuleuven.ac.be:80/cwis/research/nalag/research/topics/fitpack.html
+or
+ http://www.netlib.org/dierckx/
+
+Copyright 2002 Pearu Peterson all rights reserved,
+Pearu Peterson <[email protected]>
+Permission to use, modify, and distribute this software is given under the
+terms of the SciPy (BSD style) license. See LICENSE.txt that came with
+this distribution for specifics.
+
+NO WARRANTY IS EXPRESSED OR IMPLIED.  USE AT YOUR OWN RISK.
+
+TODO: Make interfaces to the following fitpack functions:
+    For univariate splines: cocosp, concon, fourco, insert
+    For bivariate splines: profil, regrid, parsur, surev
+"""
+
+__all__ = ['splrep', 'splprep', 'splev', 'splint', 'sproot', 'spalde',
+           'bisplrep', 'bisplev', 'insert', 'splder', 'splantider']
+
+import warnings
+import numpy as np
+from . import _fitpack
+from numpy import (atleast_1d, array, ones, zeros, sqrt, ravel, transpose,
+                   empty, iinfo, asarray)
+
+# Try to replace _fitpack interface with
+#  f2py-generated version
+from . import dfitpack
+
+
+dfitpack_int = dfitpack.types.intvar.dtype
+
+
+def _int_overflow(x, exception, msg=None):
+    """Cast the value to an dfitpack_int and raise an OverflowError if the value
+    cannot fit.
+    """
+    if x > iinfo(dfitpack_int).max:
+        if msg is None:
+            msg = f'{x!r} cannot fit into an {dfitpack_int!r}'
+        raise exception(msg)
+    return dfitpack_int.type(x)
+
+
+_iermess = {
+    0: ["The spline has a residual sum of squares fp such that "
+        "abs(fp-s)/s<=0.001", None],
+    -1: ["The spline is an interpolating spline (fp=0)", None],
+    -2: ["The spline is weighted least-squares polynomial of degree k.\n"
+         "fp gives the upper bound fp0 for the smoothing factor s", None],
+    1: ["The required storage space exceeds the available storage space.\n"
+        "Probable causes: data (x,y) size is too small or smoothing parameter"
+        "\ns is too small (fp>s).", ValueError],
+    2: ["A theoretically impossible result when finding a smoothing spline\n"
+        "with fp = s. Probable cause: s too small. (abs(fp-s)/s>0.001)",
+        ValueError],
+    3: ["The maximal number of iterations (20) allowed for finding smoothing\n"
+        "spline with fp=s has been reached. Probable cause: s too small.\n"
+        "(abs(fp-s)/s>0.001)", ValueError],
+    10: ["Error on input data", ValueError],
+    'unknown': ["An error occurred", TypeError]
+}
+
+_iermess2 = {
+    0: ["The spline has a residual sum of squares fp such that "
+        "abs(fp-s)/s<=0.001", None],
+    -1: ["The spline is an interpolating spline (fp=0)", None],
+    -2: ["The spline is weighted least-squares polynomial of degree kx and ky."
+         "\nfp gives the upper bound fp0 for the smoothing factor s", None],
+    -3: ["Warning. The coefficients of the spline have been computed as the\n"
+         "minimal norm least-squares solution of a rank deficient system.",
+         None],
+    1: ["The required storage space exceeds the available storage space.\n"
+        "Probable causes: nxest or nyest too small or s is too small. (fp>s)",
+        ValueError],
+    2: ["A theoretically impossible result when finding a smoothing spline\n"
+        "with fp = s. Probable causes: s too small or badly chosen eps.\n"
+        "(abs(fp-s)/s>0.001)", ValueError],
+    3: ["The maximal number of iterations (20) allowed for finding smoothing\n"
+        "spline with fp=s has been reached. Probable cause: s too small.\n"
+        "(abs(fp-s)/s>0.001)", ValueError],
+    4: ["No more knots can be added because the number of B-spline\n"
+        "coefficients already exceeds the number of data points m.\n"
+        "Probable causes: either s or m too small. (fp>s)", ValueError],
+    5: ["No more knots can be added because the additional knot would\n"
+        "coincide with an old one. Probable cause: s too small or too large\n"
+        "a weight to an inaccurate data point. (fp>s)", ValueError],
+    10: ["Error on input data", ValueError],
+    11: ["rwrk2 too small, i.e., there is not enough workspace for computing\n"
+         "the minimal least-squares solution of a rank deficient system of\n"
+         "linear equations.", ValueError],
+    'unknown': ["An error occurred", TypeError]
+}
+
+_parcur_cache = {'t': array([], float), 'wrk': array([], float),
+                 'iwrk': array([], dfitpack_int), 'u': array([], float),
+                 'ub': 0, 'ue': 1}
+
+
+def splprep(x, w=None, u=None, ub=None, ue=None, k=3, task=0, s=None, t=None,
+            full_output=0, nest=None, per=0, quiet=1):
+    # see the docstring of `_fitpack_py/splprep`
+    if task <= 0:
+        _parcur_cache = {'t': array([], float), 'wrk': array([], float),
+                         'iwrk': array([], dfitpack_int), 'u': array([], float),
+                         'ub': 0, 'ue': 1}
+    x = atleast_1d(x)
+    idim, m = x.shape
+    if per:
+        for i in range(idim):
+            if x[i][0] != x[i][-1]:
+                if not quiet:
+                    warnings.warn(RuntimeWarning('Setting x[%d][%d]=x[%d][0]' %
+                                                 (i, m, i)),
+                                  stacklevel=2)
+                x[i][-1] = x[i][0]
+    if not 0 < idim < 11:
+        raise TypeError('0 < idim < 11 must hold')
+    if w is None:
+        w = ones(m, float)
+    else:
+        w = atleast_1d(w)
+    ipar = (u is not None)
+    if ipar:
+        _parcur_cache['u'] = u
+        if ub is None:
+            _parcur_cache['ub'] = u[0]
+        else:
+            _parcur_cache['ub'] = ub
+        if ue is None:
+            _parcur_cache['ue'] = u[-1]
+        else:
+            _parcur_cache['ue'] = ue
+    else:
+        _parcur_cache['u'] = zeros(m, float)
+    if not (1 <= k <= 5):
+        raise TypeError('1 <= k= %d <=5 must hold' % k)
+    if not (-1 <= task <= 1):
+        raise TypeError('task must be -1, 0 or 1')
+    if (not len(w) == m) or (ipar == 1 and (not len(u) == m)):
+        raise TypeError('Mismatch of input dimensions')
+    if s is None:
+        s = m - sqrt(2*m)
+    if t is None and task == -1:
+        raise TypeError('Knots must be given for task=-1')
+    if t is not None:
+        _parcur_cache['t'] = atleast_1d(t)
+    n = len(_parcur_cache['t'])
+    if task == -1 and n < 2*k + 2:
+        raise TypeError('There must be at least 2*k+2 knots for task=-1')
+    if m <= k:
+        raise TypeError('m > k must hold')
+    if nest is None:
+        nest = m + 2*k
+
+    if (task >= 0 and s == 0) or (nest < 0):
+        if per:
+            nest = m + 2*k
+        else:
+            nest = m + k + 1
+    nest = max(nest, 2*k + 3)
+    u = _parcur_cache['u']
+    ub = _parcur_cache['ub']
+    ue = _parcur_cache['ue']
+    t = _parcur_cache['t']
+    wrk = _parcur_cache['wrk']
+    iwrk = _parcur_cache['iwrk']
+    t, c, o = _fitpack._parcur(ravel(transpose(x)), w, u, ub, ue, k,
+                               task, ipar, s, t, nest, wrk, iwrk, per)
+    _parcur_cache['u'] = o['u']
+    _parcur_cache['ub'] = o['ub']
+    _parcur_cache['ue'] = o['ue']
+    _parcur_cache['t'] = t
+    _parcur_cache['wrk'] = o['wrk']
+    _parcur_cache['iwrk'] = o['iwrk']
+    ier = o['ier']
+    fp = o['fp']
+    n = len(t)
+    u = o['u']
+    c.shape = idim, n - k - 1
+    tcku = [t, list(c), k], u
+    if ier <= 0 and not quiet:
+        warnings.warn(RuntimeWarning(_iermess[ier][0] +
+                                     "\tk=%d n=%d m=%d fp=%f s=%f" %
+                                     (k, len(t), m, fp, s)),
+                      stacklevel=2)
+    if ier > 0 and not full_output:
+        if ier in [1, 2, 3]:
+            warnings.warn(RuntimeWarning(_iermess[ier][0]), stacklevel=2)
+        else:
+            try:
+                raise _iermess[ier][1](_iermess[ier][0])
+            except KeyError as e:
+                raise _iermess['unknown'][1](_iermess['unknown'][0]) from e
+    if full_output:
+        try:
+            return tcku, fp, ier, _iermess[ier][0]
+        except KeyError:
+            return tcku, fp, ier, _iermess['unknown'][0]
+    else:
+        return tcku
+
+
+_curfit_cache = {'t': array([], float), 'wrk': array([], float),
+                 'iwrk': array([], dfitpack_int)}
+
+
+def splrep(x, y, w=None, xb=None, xe=None, k=3, task=0, s=None, t=None,
+           full_output=0, per=0, quiet=1):
+    # see the docstring of `_fitpack_py/splrep`
+    if task <= 0:
+        _curfit_cache = {}
+    x, y = map(atleast_1d, [x, y])
+    m = len(x)
+    if w is None:
+        w = ones(m, float)
+        if s is None:
+            s = 0.0
+    else:
+        w = atleast_1d(w)
+        if s is None:
+            s = m - sqrt(2*m)
+    if not len(w) == m:
+        raise TypeError('len(w)=%d is not equal to m=%d' % (len(w), m))
+    if (m != len(y)) or (m != len(w)):
+        raise TypeError('Lengths of the first three arguments (x,y,w) must '
+                        'be equal')
+    if not (1 <= k <= 5):
+        raise TypeError('Given degree of the spline (k=%d) is not supported. '
+                        '(1<=k<=5)' % k)
+    if m <= k:
+        raise TypeError('m > k must hold')
+    if xb is None:
+        xb = x[0]
+    if xe is None:
+        xe = x[-1]
+    if not (-1 <= task <= 1):
+        raise TypeError('task must be -1, 0 or 1')
+    if t is not None:
+        task = -1
+    if task == -1:
+        if t is None:
+            raise TypeError('Knots must be given for task=-1')
+        numknots = len(t)
+        _curfit_cache['t'] = empty((numknots + 2*k + 2,), float)
+        _curfit_cache['t'][k+1:-k-1] = t
+        nest = len(_curfit_cache['t'])
+    elif task == 0:
+        if per:
+            nest = max(m + 2*k, 2*k + 3)
+        else:
+            nest = max(m + k + 1, 2*k + 3)
+        t = empty((nest,), float)
+        _curfit_cache['t'] = t
+    if task <= 0:
+        if per:
+            _curfit_cache['wrk'] = empty((m*(k + 1) + nest*(8 + 5*k),), float)
+        else:
+            _curfit_cache['wrk'] = empty((m*(k + 1) + nest*(7 + 3*k),), float)
+        _curfit_cache['iwrk'] = empty((nest,), dfitpack_int)
+    try:
+        t = _curfit_cache['t']
+        wrk = _curfit_cache['wrk']
+        iwrk = _curfit_cache['iwrk']
+    except KeyError as e:
+        raise TypeError("must call with task=1 only after"
+                        " call with task=0,-1") from e
+    if not per:
+        n, c, fp, ier = dfitpack.curfit(task, x, y, w, t, wrk, iwrk,
+                                        xb, xe, k, s)
+    else:
+        n, c, fp, ier = dfitpack.percur(task, x, y, w, t, wrk, iwrk, k, s)
+    tck = (t[:n], c[:n], k)
+    if ier <= 0 and not quiet:
+        _mess = (_iermess[ier][0] + "\tk=%d n=%d m=%d fp=%f s=%f" %
+                 (k, len(t), m, fp, s))
+        warnings.warn(RuntimeWarning(_mess), stacklevel=2)
+    if ier > 0 and not full_output:
+        if ier in [1, 2, 3]:
+            warnings.warn(RuntimeWarning(_iermess[ier][0]), stacklevel=2)
+        else:
+            try:
+                raise _iermess[ier][1](_iermess[ier][0])
+            except KeyError as e:
+                raise _iermess['unknown'][1](_iermess['unknown'][0]) from e
+    if full_output:
+        try:
+            return tck, fp, ier, _iermess[ier][0]
+        except KeyError:
+            return tck, fp, ier, _iermess['unknown'][0]
+    else:
+        return tck
+
+
+def splev(x, tck, der=0, ext=0):
+    # see the docstring of `_fitpack_py/splev`
+    t, c, k = tck
+    try:
+        c[0][0]
+        parametric = True
+    except Exception:
+        parametric = False
+    if parametric:
+        return list(map(lambda c, x=x, t=t, k=k, der=der:
+                        splev(x, [t, c, k], der, ext), c))
+    else:
+        if not (0 <= der <= k):
+            raise ValueError("0<=der=%d<=k=%d must hold" % (der, k))
+        if ext not in (0, 1, 2, 3):
+            raise ValueError("ext = %s not in (0, 1, 2, 3) " % ext)
+
+        x = asarray(x)
+        shape = x.shape
+        x = atleast_1d(x).ravel()
+        if der == 0:
+            y, ier = dfitpack.splev(t, c, k, x, ext)
+        else:
+            y, ier = dfitpack.splder(t, c, k, x, der, ext)
+
+        if ier == 10:
+            raise ValueError("Invalid input data")
+        if ier == 1:
+            raise ValueError("Found x value not in the domain")
+        if ier:
+            raise TypeError("An error occurred")
+
+        return y.reshape(shape)
+
+
+def splint(a, b, tck, full_output=0):
+    # see the docstring of `_fitpack_py/splint`
+    t, c, k = tck
+    try:
+        c[0][0]
+        parametric = True
+    except Exception:
+        parametric = False
+    if parametric:
+        return list(map(lambda c, a=a, b=b, t=t, k=k:
+                        splint(a, b, [t, c, k]), c))
+    else:
+        aint, wrk = dfitpack.splint(t, c, k, a, b)
+        if full_output:
+            return aint, wrk
+        else:
+            return aint
+
+
+def sproot(tck, mest=10):
+    # see the docstring of `_fitpack_py/sproot`
+    t, c, k = tck
+    if k != 3:
+        raise ValueError("sproot works only for cubic (k=3) splines")
+    try:
+        c[0][0]
+        parametric = True
+    except Exception:
+        parametric = False
+    if parametric:
+        return list(map(lambda c, t=t, k=k, mest=mest:
+                        sproot([t, c, k], mest), c))
+    else:
+        if len(t) < 8:
+            raise TypeError("The number of knots %d>=8" % len(t))
+        z, m, ier = dfitpack.sproot(t, c, mest)
+        if ier == 10:
+            raise TypeError("Invalid input data. "
+                            "t1<=..<=t4<t5<..<tn-3<=..<=tn must hold.")
+        if ier == 0:
+            return z[:m]
+        if ier == 1:
+            warnings.warn(RuntimeWarning("The number of zeros exceeds mest"),
+                          stacklevel=2)
+            return z[:m]
+        raise TypeError("Unknown error")
+
+
+def spalde(x, tck):
+    # see the docstring of `_fitpack_py/spalde`
+    t, c, k = tck
+    try:
+        c[0][0]
+        parametric = True
+    except Exception:
+        parametric = False
+    if parametric:
+        return list(map(lambda c, x=x, t=t, k=k:
+                        spalde(x, [t, c, k]), c))
+    else:
+        x = atleast_1d(x)
+        if len(x) > 1:
+            return list(map(lambda x, tck=tck: spalde(x, tck), x))
+        d, ier = dfitpack.spalde(t, c, k+1, x[0])
+        if ier == 0:
+            return d
+        if ier == 10:
+            raise TypeError("Invalid input data. t(k)<=x<=t(n-k+1) must hold.")
+        raise TypeError("Unknown error")
+
+# def _curfit(x,y,w=None,xb=None,xe=None,k=3,task=0,s=None,t=None,
+#           full_output=0,nest=None,per=0,quiet=1):
+
+
+_surfit_cache = {'tx': array([], float), 'ty': array([], float),
+                 'wrk': array([], float), 'iwrk': array([], dfitpack_int)}
+
+
+def bisplrep(x, y, z, w=None, xb=None, xe=None, yb=None, ye=None,
+             kx=3, ky=3, task=0, s=None, eps=1e-16, tx=None, ty=None,
+             full_output=0, nxest=None, nyest=None, quiet=1):
+    """
+    Find a bivariate B-spline representation of a surface.
+
+    Given a set of data points (x[i], y[i], z[i]) representing a surface
+    z=f(x,y), compute a B-spline representation of the surface. Based on
+    the routine SURFIT from FITPACK.
+
+    Parameters
+    ----------
+    x, y, z : ndarray
+        Rank-1 arrays of data points.
+    w : ndarray, optional
+        Rank-1 array of weights. By default ``w=np.ones(len(x))``.
+    xb, xe : float, optional
+        End points of approximation interval in `x`.
+        By default ``xb = x.min(), xe=x.max()``.
+    yb, ye : float, optional
+        End points of approximation interval in `y`.
+        By default ``yb=y.min(), ye = y.max()``.
+    kx, ky : int, optional
+        The degrees of the spline (1 <= kx, ky <= 5).
+        Third order (kx=ky=3) is recommended.
+    task : int, optional
+        If task=0, find knots in x and y and coefficients for a given
+        smoothing factor, s.
+        If task=1, find knots and coefficients for another value of the
+        smoothing factor, s.  bisplrep must have been previously called
+        with task=0 or task=1.
+        If task=-1, find coefficients for a given set of knots tx, ty.
+    s : float, optional
+        A non-negative smoothing factor. If weights correspond
+        to the inverse of the standard-deviation of the errors in z,
+        then a good s-value should be found in the range
+        ``(m-sqrt(2*m),m+sqrt(2*m))`` where m=len(x).
+    eps : float, optional
+        A threshold for determining the effective rank of an
+        over-determined linear system of equations (0 < eps < 1).
+        `eps` is not likely to need changing.
+    tx, ty : ndarray, optional
+        Rank-1 arrays of the knots of the spline for task=-1
+    full_output : int, optional
+        Non-zero to return optional outputs.
+    nxest, nyest : int, optional
+        Over-estimates of the total number of knots. If None then
+        ``nxest = max(kx+sqrt(m/2),2*kx+3)``,
+        ``nyest = max(ky+sqrt(m/2),2*ky+3)``.
+    quiet : int, optional
+        Non-zero to suppress printing of messages.
+
+    Returns
+    -------
+    tck : array_like
+        A list [tx, ty, c, kx, ky] containing the knots (tx, ty) and
+        coefficients (c) of the bivariate B-spline representation of the
+        surface along with the degree of the spline.
+    fp : ndarray
+        The weighted sum of squared residuals of the spline approximation.
+    ier : int
+        An integer flag about splrep success. Success is indicated if
+        ier<=0. If ier in [1,2,3] an error occurred but was not raised.
+        Otherwise an error is raised.
+    msg : str
+        A message corresponding to the integer flag, ier.
+
+    See Also
+    --------
+    splprep, splrep, splint, sproot, splev
+    UnivariateSpline, BivariateSpline
+
+    Notes
+    -----
+    See `bisplev` to evaluate the value of the B-spline given its tck
+    representation.
+
+    If the input data is such that input dimensions have incommensurate
+    units and differ by many orders of magnitude, the interpolant may have
+    numerical artifacts. Consider rescaling the data before interpolation.
+
+    References
+    ----------
+    .. [1] Dierckx P.:An algorithm for surface fitting with spline functions
+       Ima J. Numer. Anal. 1 (1981) 267-283.
+    .. [2] Dierckx P.:An algorithm for surface fitting with spline functions
+       report tw50, Dept. Computer Science,K.U.Leuven, 1980.
+    .. [3] Dierckx P.:Curve and surface fitting with splines, Monographs on
+       Numerical Analysis, Oxford University Press, 1993.
+
+    Examples
+    --------
+    Examples are given :ref:`in the tutorial <tutorial-interpolate_2d_spline>`.
+
+    """
+    x, y, z = map(ravel, [x, y, z])  # ensure 1-d arrays.
+    m = len(x)
+    if not (m == len(y) == len(z)):
+        raise TypeError('len(x)==len(y)==len(z) must hold.')
+    if w is None:
+        w = ones(m, float)
+    else:
+        w = atleast_1d(w)
+    if not len(w) == m:
+        raise TypeError('len(w)=%d is not equal to m=%d' % (len(w), m))
+    if xb is None:
+        xb = x.min()
+    if xe is None:
+        xe = x.max()
+    if yb is None:
+        yb = y.min()
+    if ye is None:
+        ye = y.max()
+    if not (-1 <= task <= 1):
+        raise TypeError('task must be -1, 0 or 1')
+    if s is None:
+        s = m - sqrt(2*m)
+    if tx is None and task == -1:
+        raise TypeError('Knots_x must be given for task=-1')
+    if tx is not None:
+        _surfit_cache['tx'] = atleast_1d(tx)
+    nx = len(_surfit_cache['tx'])
+    if ty is None and task == -1:
+        raise TypeError('Knots_y must be given for task=-1')
+    if ty is not None:
+        _surfit_cache['ty'] = atleast_1d(ty)
+    ny = len(_surfit_cache['ty'])
+    if task == -1 and nx < 2*kx+2:
+        raise TypeError('There must be at least 2*kx+2 knots_x for task=-1')
+    if task == -1 and ny < 2*ky+2:
+        raise TypeError('There must be at least 2*ky+2 knots_x for task=-1')
+    if not ((1 <= kx <= 5) and (1 <= ky <= 5)):
+        raise TypeError('Given degree of the spline (kx,ky=%d,%d) is not '
+                        'supported. (1<=k<=5)' % (kx, ky))
+    if m < (kx + 1)*(ky + 1):
+        raise TypeError('m >= (kx+1)(ky+1) must hold')
+    if nxest is None:
+        nxest = int(kx + sqrt(m/2))
+    if nyest is None:
+        nyest = int(ky + sqrt(m/2))
+    nxest, nyest = max(nxest, 2*kx + 3), max(nyest, 2*ky + 3)
+    if task >= 0 and s == 0:
+        nxest = int(kx + sqrt(3*m))
+        nyest = int(ky + sqrt(3*m))
+    if task == -1:
+        _surfit_cache['tx'] = atleast_1d(tx)
+        _surfit_cache['ty'] = atleast_1d(ty)
+    tx, ty = _surfit_cache['tx'], _surfit_cache['ty']
+    wrk = _surfit_cache['wrk']
+    u = nxest - kx - 1
+    v = nyest - ky - 1
+    km = max(kx, ky) + 1
+    ne = max(nxest, nyest)
+    bx, by = kx*v + ky + 1, ky*u + kx + 1
+    b1, b2 = bx, bx + v - ky
+    if bx > by:
+        b1, b2 = by, by + u - kx
+    msg = "Too many data points to interpolate"
+    lwrk1 = _int_overflow(u*v*(2 + b1 + b2) +
+                          2*(u + v + km*(m + ne) + ne - kx - ky) + b2 + 1,
+                          OverflowError,
+                          msg=msg)
+    lwrk2 = _int_overflow(u*v*(b2 + 1) + b2, OverflowError, msg=msg)
+    tx, ty, c, o = _fitpack._surfit(x, y, z, w, xb, xe, yb, ye, kx, ky,
+                                    task, s, eps, tx, ty, nxest, nyest,
+                                    wrk, lwrk1, lwrk2)
+    _curfit_cache['tx'] = tx
+    _curfit_cache['ty'] = ty
+    _curfit_cache['wrk'] = o['wrk']
+    ier, fp = o['ier'], o['fp']
+    tck = [tx, ty, c, kx, ky]
+
+    ierm = min(11, max(-3, ier))
+    if ierm <= 0 and not quiet:
+        _mess = (_iermess2[ierm][0] +
+                 "\tkx,ky=%d,%d nx,ny=%d,%d m=%d fp=%f s=%f" %
+                 (kx, ky, len(tx), len(ty), m, fp, s))
+        warnings.warn(RuntimeWarning(_mess), stacklevel=2)
+    if ierm > 0 and not full_output:
+        if ier in [1, 2, 3, 4, 5]:
+            _mess = ("\n\tkx,ky=%d,%d nx,ny=%d,%d m=%d fp=%f s=%f" %
+                     (kx, ky, len(tx), len(ty), m, fp, s))
+            warnings.warn(RuntimeWarning(_iermess2[ierm][0] + _mess), stacklevel=2)
+        else:
+            try:
+                raise _iermess2[ierm][1](_iermess2[ierm][0])
+            except KeyError as e:
+                raise _iermess2['unknown'][1](_iermess2['unknown'][0]) from e
+    if full_output:
+        try:
+            return tck, fp, ier, _iermess2[ierm][0]
+        except KeyError:
+            return tck, fp, ier, _iermess2['unknown'][0]
+    else:
+        return tck
+
+
+def bisplev(x, y, tck, dx=0, dy=0):
+    """
+    Evaluate a bivariate B-spline and its derivatives.
+
+    Return a rank-2 array of spline function values (or spline derivative
+    values) at points given by the cross-product of the rank-1 arrays `x` and
+    `y`.  In special cases, return an array or just a float if either `x` or
+    `y` or both are floats.  Based on BISPEV and PARDER from FITPACK.
+
+    Parameters
+    ----------
+    x, y : ndarray
+        Rank-1 arrays specifying the domain over which to evaluate the
+        spline or its derivative.
+    tck : tuple
+        A sequence of length 5 returned by `bisplrep` containing the knot
+        locations, the coefficients, and the degree of the spline:
+        [tx, ty, c, kx, ky].
+    dx, dy : int, optional
+        The orders of the partial derivatives in `x` and `y` respectively.
+
+    Returns
+    -------
+    vals : ndarray
+        The B-spline or its derivative evaluated over the set formed by
+        the cross-product of `x` and `y`.
+
+    See Also
+    --------
+    splprep, splrep, splint, sproot, splev
+    UnivariateSpline, BivariateSpline
+
+    Notes
+    -----
+        See `bisplrep` to generate the `tck` representation.
+
+    References
+    ----------
+    .. [1] Dierckx P. : An algorithm for surface fitting
+       with spline functions
+       Ima J. Numer. Anal. 1 (1981) 267-283.
+    .. [2] Dierckx P. : An algorithm for surface fitting
+       with spline functions
+       report tw50, Dept. Computer Science,K.U.Leuven, 1980.
+    .. [3] Dierckx P. : Curve and surface fitting with splines,
+       Monographs on Numerical Analysis, Oxford University Press, 1993.
+
+    Examples
+    --------
+    Examples are given :ref:`in the tutorial <tutorial-interpolate_2d_spline>`.
+
+    """
+    tx, ty, c, kx, ky = tck
+    if not (0 <= dx < kx):
+        raise ValueError("0 <= dx = %d < kx = %d must hold" % (dx, kx))
+    if not (0 <= dy < ky):
+        raise ValueError("0 <= dy = %d < ky = %d must hold" % (dy, ky))
+    x, y = map(atleast_1d, [x, y])
+    if (len(x.shape) != 1) or (len(y.shape) != 1):
+        raise ValueError("First two entries should be rank-1 arrays.")
+
+    msg = "Too many data points to interpolate."
+
+    _int_overflow(x.size * y.size, MemoryError, msg=msg)
+
+    if dx != 0 or dy != 0:
+        _int_overflow((tx.size - kx - 1)*(ty.size - ky - 1),
+                      MemoryError, msg=msg)
+        z, ier = dfitpack.parder(tx, ty, c, kx, ky, dx, dy, x, y)
+    else:
+        z, ier = dfitpack.bispev(tx, ty, c, kx, ky, x, y)
+
+    if ier == 10:
+        raise ValueError("Invalid input data")
+    if ier:
+        raise TypeError("An error occurred")
+    z.shape = len(x), len(y)
+    if len(z) > 1:
+        return z
+    if len(z[0]) > 1:
+        return z[0]
+    return z[0][0]
+
+
+def dblint(xa, xb, ya, yb, tck):
+    """Evaluate the integral of a spline over area [xa,xb] x [ya,yb].
+
+    Parameters
+    ----------
+    xa, xb : float
+        The end-points of the x integration interval.
+    ya, yb : float
+        The end-points of the y integration interval.
+    tck : list [tx, ty, c, kx, ky]
+        A sequence of length 5 returned by bisplrep containing the knot
+        locations tx, ty, the coefficients c, and the degrees kx, ky
+        of the spline.
+
+    Returns
+    -------
+    integ : float
+        The value of the resulting integral.
+    """
+    tx, ty, c, kx, ky = tck
+    return dfitpack.dblint(tx, ty, c, kx, ky, xa, xb, ya, yb)
+
+
+def insert(x, tck, m=1, per=0):
+    # see the docstring of `_fitpack_py/insert`
+    t, c, k = tck
+    try:
+        c[0][0]
+        parametric = True
+    except Exception:
+        parametric = False
+    if parametric:
+        cc = []
+        for c_vals in c:
+            tt, cc_val, kk = insert(x, [t, c_vals, k], m)
+            cc.append(cc_val)
+        return (tt, cc, kk)
+    else:
+        tt, cc, ier = _fitpack._insert(per, t, c, k, x, m)
+        if ier == 10:
+            raise ValueError("Invalid input data")
+        if ier:
+            raise TypeError("An error occurred")
+        return (tt, cc, k)
+
+
+def splder(tck, n=1):
+    # see the docstring of `_fitpack_py/splder`
+    if n < 0:
+        return splantider(tck, -n)
+
+    t, c, k = tck
+
+    if n > k:
+        raise ValueError(f"Order of derivative (n = {n!r}) must be <= "
+                         f"order of spline (k = {tck[2]!r})")
+
+    # Extra axes for the trailing dims of the `c` array:
+    sh = (slice(None),) + ((None,)*len(c.shape[1:]))
+
+    with np.errstate(invalid='raise', divide='raise'):
+        try:
+            for j in range(n):
+                # See e.g. Schumaker, Spline Functions: Basic Theory, Chapter 5
+
+                # Compute the denominator in the differentiation formula.
+                # (and append trailing dims, if necessary)
+                dt = t[k+1:-1] - t[1:-k-1]
+                dt = dt[sh]
+                # Compute the new coefficients
+                c = (c[1:-1-k] - c[:-2-k]) * k / dt
+                # Pad coefficient array to same size as knots (FITPACK
+                # convention)
+                c = np.r_[c, np.zeros((k,) + c.shape[1:])]
+                # Adjust knots
+                t = t[1:-1]
+                k -= 1
+        except FloatingPointError as e:
+            raise ValueError(("The spline has internal repeated knots "
+                              "and is not differentiable %d times") % n) from e
+
+    return t, c, k
+
+
+def splantider(tck, n=1):
+    # see the docstring of `_fitpack_py/splantider`
+    if n < 0:
+        return splder(tck, -n)
+
+    t, c, k = tck
+
+    # Extra axes for the trailing dims of the `c` array:
+    sh = (slice(None),) + (None,)*len(c.shape[1:])
+
+    for j in range(n):
+        # This is the inverse set of operations to splder.
+
+        # Compute the multiplier in the antiderivative formula.
+        dt = t[k+1:] - t[:-k-1]
+        dt = dt[sh]
+        # Compute the new coefficients
+        c = np.cumsum(c[:-k-1] * dt, axis=0) / (k + 1)
+        c = np.r_[np.zeros((1,) + c.shape[1:]),
+                  c,
+                  [c[-1]] * (k+2)]
+        # New knots
+        t = np.r_[t[0], t, t[-1]]
+        k += 1
+
+    return t, c, k

venv/lib/python3.10/site-packages/scipy/interpolate/_fitpack_py.py

@@ -0,0 +1,796 @@
+__all__ = ['splrep', 'splprep', 'splev', 'splint', 'sproot', 'spalde',
+           'bisplrep', 'bisplev', 'insert', 'splder', 'splantider']
+
+
+import numpy as np
+
+# These are in the API for fitpack even if not used in fitpack.py itself.
+from ._fitpack_impl import bisplrep, bisplev, dblint  # noqa: F401
+from . import _fitpack_impl as _impl
+from ._bsplines import BSpline
+
+
+def splprep(x, w=None, u=None, ub=None, ue=None, k=3, task=0, s=None, t=None,
+            full_output=0, nest=None, per=0, quiet=1):
+    """
+    Find the B-spline representation of an N-D curve.
+
+    Given a list of N rank-1 arrays, `x`, which represent a curve in
+    N-dimensional space parametrized by `u`, find a smooth approximating
+    spline curve g(`u`). Uses the FORTRAN routine parcur from FITPACK.
+
+    Parameters
+    ----------
+    x : array_like
+        A list of sample vector arrays representing the curve.
+    w : array_like, optional
+        Strictly positive rank-1 array of weights the same length as `x[0]`.
+        The weights are used in computing the weighted least-squares spline
+        fit. If the errors in the `x` values have standard-deviation given by
+        the vector d, then `w` should be 1/d. Default is ``ones(len(x[0]))``.
+    u : array_like, optional
+        An array of parameter values. If not given, these values are
+        calculated automatically as ``M = len(x[0])``, where
+
+            v[0] = 0
+
+            v[i] = v[i-1] + distance(`x[i]`, `x[i-1]`)
+
+            u[i] = v[i] / v[M-1]
+
+    ub, ue : int, optional
+        The end-points of the parameters interval.  Defaults to
+        u[0] and u[-1].
+    k : int, optional
+        Degree of the spline. Cubic splines are recommended.
+        Even values of `k` should be avoided especially with a small s-value.
+        ``1 <= k <= 5``, default is 3.
+    task : int, optional
+        If task==0 (default), find t and c for a given smoothing factor, s.
+        If task==1, find t and c for another value of the smoothing factor, s.
+        There must have been a previous call with task=0 or task=1
+        for the same set of data.
+        If task=-1 find the weighted least square spline for a given set of
+        knots, t.
+    s : float, optional
+        A smoothing condition.  The amount of smoothness is determined by
+        satisfying the conditions: ``sum((w * (y - g))**2,axis=0) <= s``,
+        where g(x) is the smoothed interpolation of (x,y).  The user can
+        use `s` to control the trade-off between closeness and smoothness
+        of fit.  Larger `s` means more smoothing while smaller values of `s`
+        indicate less smoothing. Recommended values of `s` depend on the
+        weights, w.  If the weights represent the inverse of the
+        standard-deviation of y, then a good `s` value should be found in
+        the range ``(m-sqrt(2*m),m+sqrt(2*m))``, where m is the number of
+        data points in x, y, and w.
+    t : array, optional
+        The knots needed for ``task=-1``.
+        There must be at least ``2*k+2`` knots.
+    full_output : int, optional
+        If non-zero, then return optional outputs.
+    nest : int, optional
+        An over-estimate of the total number of knots of the spline to
+        help in determining the storage space.  By default nest=m/2.
+        Always large enough is nest=m+k+1.
+    per : int, optional
+       If non-zero, data points are considered periodic with period
+       ``x[m-1] - x[0]`` and a smooth periodic spline approximation is
+       returned.  Values of ``y[m-1]`` and ``w[m-1]`` are not used.
+    quiet : int, optional
+         Non-zero to suppress messages.
+
+    Returns
+    -------
+    tck : tuple
+        A tuple, ``(t,c,k)`` containing the vector of knots, the B-spline
+        coefficients, and the degree of the spline.
+    u : array
+        An array of the values of the parameter.
+    fp : float
+        The weighted sum of squared residuals of the spline approximation.
+    ier : int
+        An integer flag about splrep success.  Success is indicated
+        if ier<=0. If ier in [1,2,3] an error occurred but was not raised.
+        Otherwise an error is raised.
+    msg : str
+        A message corresponding to the integer flag, ier.
+
+    See Also
+    --------
+    splrep, splev, sproot, spalde, splint,
+    bisplrep, bisplev
+    UnivariateSpline, BivariateSpline
+    BSpline
+    make_interp_spline
+
+    Notes
+    -----
+    See `splev` for evaluation of the spline and its derivatives.
+    The number of dimensions N must be smaller than 11.
+
+    The number of coefficients in the `c` array is ``k+1`` less than the number
+    of knots, ``len(t)``. This is in contrast with `splrep`, which zero-pads
+    the array of coefficients to have the same length as the array of knots.
+    These additional coefficients are ignored by evaluation routines, `splev`
+    and `BSpline`.
+
+    References
+    ----------
+    .. [1] P. Dierckx, "Algorithms for smoothing data with periodic and
+        parametric splines, Computer Graphics and Image Processing",
+        20 (1982) 171-184.
+    .. [2] P. Dierckx, "Algorithms for smoothing data with periodic and
+        parametric splines", report tw55, Dept. Computer Science,
+        K.U.Leuven, 1981.
+    .. [3] P. Dierckx, "Curve and surface fitting with splines", Monographs on
+        Numerical Analysis, Oxford University Press, 1993.
+
+    Examples
+    --------
+    Generate a discretization of a limacon curve in the polar coordinates:
+
+    >>> import numpy as np
+    >>> phi = np.linspace(0, 2.*np.pi, 40)
+    >>> r = 0.5 + np.cos(phi)         # polar coords
+    >>> x, y = r * np.cos(phi), r * np.sin(phi)    # convert to cartesian
+
+    And interpolate:
+
+    >>> from scipy.interpolate import splprep, splev
+    >>> tck, u = splprep([x, y], s=0)
+    >>> new_points = splev(u, tck)
+
+    Notice that (i) we force interpolation by using `s=0`,
+    (ii) the parameterization, ``u``, is generated automatically.
+    Now plot the result:
+
+    >>> import matplotlib.pyplot as plt
+    >>> fig, ax = plt.subplots()
+    >>> ax.plot(x, y, 'ro')
+    >>> ax.plot(new_points[0], new_points[1], 'r-')
+    >>> plt.show()
+
+    """
+
+    res = _impl.splprep(x, w, u, ub, ue, k, task, s, t, full_output, nest, per,
+                        quiet)
+    return res
+
+
+def splrep(x, y, w=None, xb=None, xe=None, k=3, task=0, s=None, t=None,
+           full_output=0, per=0, quiet=1):
+    """
+    Find the B-spline representation of a 1-D curve.
+
+    Given the set of data points ``(x[i], y[i])`` determine a smooth spline
+    approximation of degree k on the interval ``xb <= x <= xe``.
+
+    Parameters
+    ----------
+    x, y : array_like
+        The data points defining a curve ``y = f(x)``.
+    w : array_like, optional
+        Strictly positive rank-1 array of weights the same length as `x` and `y`.
+        The weights are used in computing the weighted least-squares spline
+        fit. If the errors in the `y` values have standard-deviation given by the
+        vector ``d``, then `w` should be ``1/d``. Default is ``ones(len(x))``.
+    xb, xe : float, optional
+        The interval to fit.  If None, these default to ``x[0]`` and ``x[-1]``
+        respectively.
+    k : int, optional
+        The degree of the spline fit. It is recommended to use cubic splines.
+        Even values of `k` should be avoided especially with small `s` values.
+        ``1 <= k <= 5``.
+    task : {1, 0, -1}, optional
+        If ``task==0``, find ``t`` and ``c`` for a given smoothing factor, `s`.
+
+        If ``task==1`` find ``t`` and ``c`` for another value of the smoothing factor,
+        `s`. There must have been a previous call with ``task=0`` or ``task=1`` for
+        the same set of data (``t`` will be stored an used internally)
+
+        If ``task=-1`` find the weighted least square spline for a given set of
+        knots, ``t``. These should be interior knots as knots on the ends will be
+        added automatically.
+    s : float, optional
+        A smoothing condition. The amount of smoothness is determined by
+        satisfying the conditions: ``sum((w * (y - g))**2,axis=0) <= s`` where ``g(x)``
+        is the smoothed interpolation of ``(x,y)``. The user can use `s` to control
+        the tradeoff between closeness and smoothness of fit. Larger `s` means
+        more smoothing while smaller values of `s` indicate less smoothing.
+        Recommended values of `s` depend on the weights, `w`. If the weights
+        represent the inverse of the standard-deviation of `y`, then a good `s`
+        value should be found in the range ``(m-sqrt(2*m),m+sqrt(2*m))`` where ``m`` is
+        the number of datapoints in `x`, `y`, and `w`. default : ``s=m-sqrt(2*m)`` if
+        weights are supplied. ``s = 0.0`` (interpolating) if no weights are
+        supplied.
+    t : array_like, optional
+        The knots needed for ``task=-1``. If given then task is automatically set
+        to ``-1``.
+    full_output : bool, optional
+        If non-zero, then return optional outputs.
+    per : bool, optional
+        If non-zero, data points are considered periodic with period ``x[m-1]`` -
+        ``x[0]`` and a smooth periodic spline approximation is returned. Values of
+        ``y[m-1]`` and ``w[m-1]`` are not used.
+        The default is zero, corresponding to boundary condition 'not-a-knot'.
+    quiet : bool, optional
+        Non-zero to suppress messages.
+
+    Returns
+    -------
+    tck : tuple
+        A tuple ``(t,c,k)`` containing the vector of knots, the B-spline
+        coefficients, and the degree of the spline.
+    fp : array, optional
+        The weighted sum of squared residuals of the spline approximation.
+    ier : int, optional
+        An integer flag about splrep success. Success is indicated if ``ier<=0``.
+        If ``ier in [1,2,3]``, an error occurred but was not raised. Otherwise an
+        error is raised.
+    msg : str, optional
+        A message corresponding to the integer flag, `ier`.
+
+    See Also
+    --------
+    UnivariateSpline, BivariateSpline
+    splprep, splev, sproot, spalde, splint
+    bisplrep, bisplev
+    BSpline
+    make_interp_spline
+
+    Notes
+    -----
+    See `splev` for evaluation of the spline and its derivatives. Uses the
+    FORTRAN routine ``curfit`` from FITPACK.
+
+    The user is responsible for assuring that the values of `x` are unique.
+    Otherwise, `splrep` will not return sensible results.
+
+    If provided, knots `t` must satisfy the Schoenberg-Whitney conditions,
+    i.e., there must be a subset of data points ``x[j]`` such that
+    ``t[j] < x[j] < t[j+k+1]``, for ``j=0, 1,...,n-k-2``.
+
+    This routine zero-pads the coefficients array ``c`` to have the same length
+    as the array of knots ``t`` (the trailing ``k + 1`` coefficients are ignored
+    by the evaluation routines, `splev` and `BSpline`.) This is in contrast with
+    `splprep`, which does not zero-pad the coefficients.
+
+    The default boundary condition is 'not-a-knot', i.e. the first and second
+    segment at a curve end are the same polynomial. More boundary conditions are
+    available in `CubicSpline`.
+
+    References
+    ----------
+    Based on algorithms described in [1]_, [2]_, [3]_, and [4]_:
+
+    .. [1] P. Dierckx, "An algorithm for smoothing, differentiation and
+       integration of experimental data using spline functions",
+       J.Comp.Appl.Maths 1 (1975) 165-184.
+    .. [2] P. Dierckx, "A fast algorithm for smoothing data on a rectangular
+       grid while using spline functions", SIAM J.Numer.Anal. 19 (1982)
+       1286-1304.
+    .. [3] P. Dierckx, "An improved algorithm for curve fitting with spline
+       functions", report tw54, Dept. Computer Science,K.U. Leuven, 1981.
+    .. [4] P. Dierckx, "Curve and surface fitting with splines", Monographs on
+       Numerical Analysis, Oxford University Press, 1993.
+
+    Examples
+    --------
+    You can interpolate 1-D points with a B-spline curve.
+    Further examples are given in
+    :ref:`in the tutorial <tutorial-interpolate_splXXX>`.
+
+    >>> import numpy as np
+    >>> import matplotlib.pyplot as plt
+    >>> from scipy.interpolate import splev, splrep
+    >>> x = np.linspace(0, 10, 10)
+    >>> y = np.sin(x)
+    >>> spl = splrep(x, y)
+    >>> x2 = np.linspace(0, 10, 200)
+    >>> y2 = splev(x2, spl)
+    >>> plt.plot(x, y, 'o', x2, y2)
+    >>> plt.show()
+
+    """
+    res = _impl.splrep(x, y, w, xb, xe, k, task, s, t, full_output, per, quiet)
+    return res
+
+
+def splev(x, tck, der=0, ext=0):
+    """
+    Evaluate a B-spline or its derivatives.
+
+    Given the knots and coefficients of a B-spline representation, evaluate
+    the value of the smoothing polynomial and its derivatives. This is a
+    wrapper around the FORTRAN routines splev and splder of FITPACK.
+
+    Parameters
+    ----------
+    x : array_like
+        An array of points at which to return the value of the smoothed
+        spline or its derivatives. If `tck` was returned from `splprep`,
+        then the parameter values, u should be given.
+    tck : 3-tuple or a BSpline object
+        If a tuple, then it should be a sequence of length 3 returned by
+        `splrep` or `splprep` containing the knots, coefficients, and degree
+        of the spline. (Also see Notes.)
+    der : int, optional
+        The order of derivative of the spline to compute (must be less than
+        or equal to k, the degree of the spline).
+    ext : int, optional
+        Controls the value returned for elements of ``x`` not in the
+        interval defined by the knot sequence.
+
+        * if ext=0, return the extrapolated value.
+        * if ext=1, return 0
+        * if ext=2, raise a ValueError
+        * if ext=3, return the boundary value.
+
+        The default value is 0.
+
+    Returns
+    -------
+    y : ndarray or list of ndarrays
+        An array of values representing the spline function evaluated at
+        the points in `x`.  If `tck` was returned from `splprep`, then this
+        is a list of arrays representing the curve in an N-D space.
+
+    See Also
+    --------
+    splprep, splrep, sproot, spalde, splint
+    bisplrep, bisplev
+    BSpline
+
+    Notes
+    -----
+    Manipulating the tck-tuples directly is not recommended. In new code,
+    prefer using `BSpline` objects.
+
+    References
+    ----------
+    .. [1] C. de Boor, "On calculating with b-splines", J. Approximation
+        Theory, 6, p.50-62, 1972.
+    .. [2] M. G. Cox, "The numerical evaluation of b-splines", J. Inst. Maths
+        Applics, 10, p.134-149, 1972.
+    .. [3] P. Dierckx, "Curve and surface fitting with splines", Monographs
+        on Numerical Analysis, Oxford University Press, 1993.
+
+    Examples
+    --------
+    Examples are given :ref:`in the tutorial <tutorial-interpolate_splXXX>`.
+
+    """
+    if isinstance(tck, BSpline):
+        if tck.c.ndim > 1:
+            mesg = ("Calling splev() with BSpline objects with c.ndim > 1 is "
+                    "not allowed. Use BSpline.__call__(x) instead.")
+            raise ValueError(mesg)
+
+        # remap the out-of-bounds behavior
+        try:
+            extrapolate = {0: True, }[ext]
+        except KeyError as e:
+            raise ValueError("Extrapolation mode %s is not supported "
+                             "by BSpline." % ext) from e
+
+        return tck(x, der, extrapolate=extrapolate)
+    else:
+        return _impl.splev(x, tck, der, ext)
+
+
+def splint(a, b, tck, full_output=0):
+    """
+    Evaluate the definite integral of a B-spline between two given points.
+
+    Parameters
+    ----------
+    a, b : float
+        The end-points of the integration interval.
+    tck : tuple or a BSpline instance
+        If a tuple, then it should be a sequence of length 3, containing the
+        vector of knots, the B-spline coefficients, and the degree of the
+        spline (see `splev`).
+    full_output : int, optional
+        Non-zero to return optional output.
+
+    Returns
+    -------
+    integral : float
+        The resulting integral.
+    wrk : ndarray
+        An array containing the integrals of the normalized B-splines
+        defined on the set of knots.
+        (Only returned if `full_output` is non-zero)
+
+    See Also
+    --------
+    splprep, splrep, sproot, spalde, splev
+    bisplrep, bisplev
+    BSpline
+
+    Notes
+    -----
+    `splint` silently assumes that the spline function is zero outside the data
+    interval (`a`, `b`).
+
+    Manipulating the tck-tuples directly is not recommended. In new code,
+    prefer using the `BSpline` objects.
+
+    References
+    ----------
+    .. [1] P.W. Gaffney, The calculation of indefinite integrals of b-splines",
+        J. Inst. Maths Applics, 17, p.37-41, 1976.
+    .. [2] P. Dierckx, "Curve and surface fitting with splines", Monographs
+        on Numerical Analysis, Oxford University Press, 1993.
+
+    Examples
+    --------
+    Examples are given :ref:`in the tutorial <tutorial-interpolate_splXXX>`.
+
+    """
+    if isinstance(tck, BSpline):
+        if tck.c.ndim > 1:
+            mesg = ("Calling splint() with BSpline objects with c.ndim > 1 is "
+                    "not allowed. Use BSpline.integrate() instead.")
+            raise ValueError(mesg)
+
+        if full_output != 0:
+            mesg = ("full_output = %s is not supported. Proceeding as if "
+                    "full_output = 0" % full_output)
+
+        return tck.integrate(a, b, extrapolate=False)
+    else:
+        return _impl.splint(a, b, tck, full_output)
+
+
+def sproot(tck, mest=10):
+    """
+    Find the roots of a cubic B-spline.
+
+    Given the knots (>=8) and coefficients of a cubic B-spline return the
+    roots of the spline.
+
+    Parameters
+    ----------
+    tck : tuple or a BSpline object
+        If a tuple, then it should be a sequence of length 3, containing the
+        vector of knots, the B-spline coefficients, and the degree of the
+        spline.
+        The number of knots must be >= 8, and the degree must be 3.
+        The knots must be a montonically increasing sequence.
+    mest : int, optional
+        An estimate of the number of zeros (Default is 10).
+
+    Returns
+    -------
+    zeros : ndarray
+        An array giving the roots of the spline.
+
+    See Also
+    --------
+    splprep, splrep, splint, spalde, splev
+    bisplrep, bisplev
+    BSpline
+
+    Notes
+    -----
+    Manipulating the tck-tuples directly is not recommended. In new code,
+    prefer using the `BSpline` objects.
+
+    References
+    ----------
+    .. [1] C. de Boor, "On calculating with b-splines", J. Approximation
+        Theory, 6, p.50-62, 1972.
+    .. [2] M. G. Cox, "The numerical evaluation of b-splines", J. Inst. Maths
+        Applics, 10, p.134-149, 1972.
+    .. [3] P. Dierckx, "Curve and surface fitting with splines", Monographs
+        on Numerical Analysis, Oxford University Press, 1993.
+
+    Examples
+    --------
+
+    For some data, this method may miss a root. This happens when one of
+    the spline knots (which FITPACK places automatically) happens to
+    coincide with the true root. A workaround is to convert to `PPoly`,
+    which uses a different root-finding algorithm.
+
+    For example,
+
+    >>> x = [1.96, 1.97, 1.98, 1.99, 2.00, 2.01, 2.02, 2.03, 2.04, 2.05]
+    >>> y = [-6.365470e-03, -4.790580e-03, -3.204320e-03, -1.607270e-03,
+    ...      4.440892e-16,  1.616930e-03,  3.243000e-03,  4.877670e-03,
+    ...      6.520430e-03,  8.170770e-03]
+    >>> from scipy.interpolate import splrep, sproot, PPoly
+    >>> tck = splrep(x, y, s=0)
+    >>> sproot(tck)
+    array([], dtype=float64)
+
+    Converting to a PPoly object does find the roots at `x=2`:
+
+    >>> ppoly = PPoly.from_spline(tck)
+    >>> ppoly.roots(extrapolate=False)
+    array([2.])
+
+
+    Further examples are given :ref:`in the tutorial
+    <tutorial-interpolate_splXXX>`.
+
+    """
+    if isinstance(tck, BSpline):
+        if tck.c.ndim > 1:
+            mesg = ("Calling sproot() with BSpline objects with c.ndim > 1 is "
+                    "not allowed.")
+            raise ValueError(mesg)
+
+        t, c, k = tck.tck
+
+        # _impl.sproot expects the interpolation axis to be last, so roll it.
+        # NB: This transpose is a no-op if c is 1D.
+        sh = tuple(range(c.ndim))
+        c = c.transpose(sh[1:] + (0,))
+        return _impl.sproot((t, c, k), mest)
+    else:
+        return _impl.sproot(tck, mest)
+
+
+def spalde(x, tck):
+    """
+    Evaluate all derivatives of a B-spline.
+
+    Given the knots and coefficients of a cubic B-spline compute all
+    derivatives up to order k at a point (or set of points).
+
+    Parameters
+    ----------
+    x : array_like
+        A point or a set of points at which to evaluate the derivatives.
+        Note that ``t(k) <= x <= t(n-k+1)`` must hold for each `x`.
+    tck : tuple
+        A tuple (t,c,k) containing the vector of knots,
+        the B-spline coefficients, and the degree of the spline.
+
+    Returns
+    -------
+    results : {ndarray, list of ndarrays}
+        An array (or a list of arrays) containing all derivatives
+        up to order k inclusive for each point `x`.
+
+    See Also
+    --------
+    splprep, splrep, splint, sproot, splev, bisplrep, bisplev,
+    UnivariateSpline, BivariateSpline
+
+    References
+    ----------
+    .. [1] de Boor C : On calculating with b-splines, J. Approximation Theory
+       6 (1972) 50-62.
+    .. [2] Cox M.G. : The numerical evaluation of b-splines, J. Inst. Maths
+       applics 10 (1972) 134-149.
+    .. [3] Dierckx P. : Curve and surface fitting with splines, Monographs on
+       Numerical Analysis, Oxford University Press, 1993.
+
+    """
+    if isinstance(tck, BSpline):
+        raise TypeError("spalde does not accept BSpline instances.")
+    else:
+        return _impl.spalde(x, tck)
+
+
+def insert(x, tck, m=1, per=0):
+    """
+    Insert knots into a B-spline.
+
+    Given the knots and coefficients of a B-spline representation, create a
+    new B-spline with a knot inserted `m` times at point `x`.
+    This is a wrapper around the FORTRAN routine insert of FITPACK.
+
+    Parameters
+    ----------
+    x (u) : float
+        A knot value at which to insert a new knot.  If `tck` was returned
+        from ``splprep``, then the parameter values, u should be given.
+    tck : a `BSpline` instance or a tuple
+        If tuple, then it is expected to be a tuple (t,c,k) containing
+        the vector of knots, the B-spline coefficients, and the degree of
+        the spline.
+    m : int, optional
+        The number of times to insert the given knot (its multiplicity).
+        Default is 1.
+    per : int, optional
+        If non-zero, the input spline is considered periodic.
+
+    Returns
+    -------
+    BSpline instance or a tuple
+        A new B-spline with knots t, coefficients c, and degree k.
+        ``t(k+1) <= x <= t(n-k)``, where k is the degree of the spline.
+        In case of a periodic spline (``per != 0``) there must be
+        either at least k interior knots t(j) satisfying ``t(k+1)<t(j)<=x``
+        or at least k interior knots t(j) satisfying ``x<=t(j)<t(n-k)``.
+        A tuple is returned iff the input argument `tck` is a tuple, otherwise
+        a BSpline object is constructed and returned.
+
+    Notes
+    -----
+    Based on algorithms from [1]_ and [2]_.
+
+    Manipulating the tck-tuples directly is not recommended. In new code,
+    prefer using the `BSpline` objects, in particular `BSpline.insert_knot`
+    method.
+
+    See Also
+    --------
+    BSpline.insert_knot
+
+    References
+    ----------
+    .. [1] W. Boehm, "Inserting new knots into b-spline curves.",
+        Computer Aided Design, 12, p.199-201, 1980.
+    .. [2] P. Dierckx, "Curve and surface fitting with splines, Monographs on
+        Numerical Analysis", Oxford University Press, 1993.
+
+    Examples
+    --------
+    You can insert knots into a B-spline.
+
+    >>> from scipy.interpolate import splrep, insert
+    >>> import numpy as np
+    >>> x = np.linspace(0, 10, 5)
+    >>> y = np.sin(x)
+    >>> tck = splrep(x, y)
+    >>> tck[0]
+    array([ 0.,  0.,  0.,  0.,  5., 10., 10., 10., 10.])
+
+    A knot is inserted:
+
+    >>> tck_inserted = insert(3, tck)
+    >>> tck_inserted[0]
+    array([ 0.,  0.,  0.,  0.,  3.,  5., 10., 10., 10., 10.])
+
+    Some knots are inserted:
+
+    >>> tck_inserted2 = insert(8, tck, m=3)
+    >>> tck_inserted2[0]
+    array([ 0.,  0.,  0.,  0.,  5.,  8.,  8.,  8., 10., 10., 10., 10.])
+
+    """
+    if isinstance(tck, BSpline):
+
+        t, c, k = tck.tck
+
+        # FITPACK expects the interpolation axis to be last, so roll it over
+        # NB: if c array is 1D, transposes are no-ops
+        sh = tuple(range(c.ndim))
+        c = c.transpose(sh[1:] + (0,))
+        t_, c_, k_ = _impl.insert(x, (t, c, k), m, per)
+
+        # and roll the last axis back
+        c_ = np.asarray(c_)
+        c_ = c_.transpose((sh[-1],) + sh[:-1])
+        return BSpline(t_, c_, k_)
+    else:
+        return _impl.insert(x, tck, m, per)
+
+
+def splder(tck, n=1):
+    """
+    Compute the spline representation of the derivative of a given spline
+
+    Parameters
+    ----------
+    tck : BSpline instance or a tuple of (t, c, k)
+        Spline whose derivative to compute
+    n : int, optional
+        Order of derivative to evaluate. Default: 1
+
+    Returns
+    -------
+    `BSpline` instance or tuple
+        Spline of order k2=k-n representing the derivative
+        of the input spline.
+        A tuple is returned iff the input argument `tck` is a tuple, otherwise
+        a BSpline object is constructed and returned.
+
+    See Also
+    --------
+    splantider, splev, spalde
+    BSpline
+
+    Notes
+    -----
+
+    .. versionadded:: 0.13.0
+
+    Examples
+    --------
+    This can be used for finding maxima of a curve:
+
+    >>> from scipy.interpolate import splrep, splder, sproot
+    >>> import numpy as np
+    >>> x = np.linspace(0, 10, 70)
+    >>> y = np.sin(x)
+    >>> spl = splrep(x, y, k=4)
+
+    Now, differentiate the spline and find the zeros of the
+    derivative. (NB: `sproot` only works for order 3 splines, so we
+    fit an order 4 spline):
+
+    >>> dspl = splder(spl)
+    >>> sproot(dspl) / np.pi
+    array([ 0.50000001,  1.5       ,  2.49999998])
+
+    This agrees well with roots :math:`\\pi/2 + n\\pi` of
+    :math:`\\cos(x) = \\sin'(x)`.
+
+    """
+    if isinstance(tck, BSpline):
+        return tck.derivative(n)
+    else:
+        return _impl.splder(tck, n)
+
+
+def splantider(tck, n=1):
+    """
+    Compute the spline for the antiderivative (integral) of a given spline.
+
+    Parameters
+    ----------
+    tck : BSpline instance or a tuple of (t, c, k)
+        Spline whose antiderivative to compute
+    n : int, optional
+        Order of antiderivative to evaluate. Default: 1
+
+    Returns
+    -------
+    BSpline instance or a tuple of (t2, c2, k2)
+        Spline of order k2=k+n representing the antiderivative of the input
+        spline.
+        A tuple is returned iff the input argument `tck` is a tuple, otherwise
+        a BSpline object is constructed and returned.
+
+    See Also
+    --------
+    splder, splev, spalde
+    BSpline
+
+    Notes
+    -----
+    The `splder` function is the inverse operation of this function.
+    Namely, ``splder(splantider(tck))`` is identical to `tck`, modulo
+    rounding error.
+
+    .. versionadded:: 0.13.0
+
+    Examples
+    --------
+    >>> from scipy.interpolate import splrep, splder, splantider, splev
+    >>> import numpy as np
+    >>> x = np.linspace(0, np.pi/2, 70)
+    >>> y = 1 / np.sqrt(1 - 0.8*np.sin(x)**2)
+    >>> spl = splrep(x, y)
+
+    The derivative is the inverse operation of the antiderivative,
+    although some floating point error accumulates:
+
+    >>> splev(1.7, spl), splev(1.7, splder(splantider(spl)))
+    (array(2.1565429877197317), array(2.1565429877201865))
+
+    Antiderivative can be used to evaluate definite integrals:
+
+    >>> ispl = splantider(spl)
+    >>> splev(np.pi/2, ispl) - splev(0, ispl)
+    2.2572053588768486
+
+    This is indeed an approximation to the complete elliptic integral
+    :math:`K(m) = \\int_0^{\\pi/2} [1 - m\\sin^2 x]^{-1/2} dx`:
+
+    >>> from scipy.special import ellipk
+    >>> ellipk(0.8)
+    2.2572053268208538
+
+    """
+    if isinstance(tck, BSpline):
+        return tck.antiderivative(n)
+    else:
+        return _impl.splantider(tck, n)
+

venv/lib/python3.10/site-packages/scipy/interpolate/_interpolate.py

@@ -0,0 +1,2473 @@
+__all__ = ['interp1d', 'interp2d', 'lagrange', 'PPoly', 'BPoly', 'NdPPoly']
+
+from math import prod
+import warnings
+
+import numpy as np
+from numpy import (array, transpose, searchsorted, atleast_1d, atleast_2d,
+                   ravel, poly1d, asarray, intp)
+
+import scipy.special as spec
+from scipy._lib._util import copy_if_needed
+from scipy.special import comb
+
+from . import _fitpack_py
+from . import dfitpack
+from ._polyint import _Interpolator1D
+from . import _ppoly
+from .interpnd import _ndim_coords_from_arrays
+from ._bsplines import make_interp_spline, BSpline
+
+
+def lagrange(x, w):
+    r"""
+    Return a Lagrange interpolating polynomial.
+
+    Given two 1-D arrays `x` and `w,` returns the Lagrange interpolating
+    polynomial through the points ``(x, w)``.
+
+    Warning: This implementation is numerically unstable. Do not expect to
+    be able to use more than about 20 points even if they are chosen optimally.
+
+    Parameters
+    ----------
+    x : array_like
+        `x` represents the x-coordinates of a set of datapoints.
+    w : array_like
+        `w` represents the y-coordinates of a set of datapoints, i.e., f(`x`).
+
+    Returns
+    -------
+    lagrange : `numpy.poly1d` instance
+        The Lagrange interpolating polynomial.
+
+    Examples
+    --------
+    Interpolate :math:`f(x) = x^3` by 3 points.
+
+    >>> import numpy as np
+    >>> from scipy.interpolate import lagrange
+    >>> x = np.array([0, 1, 2])
+    >>> y = x**3
+    >>> poly = lagrange(x, y)
+
+    Since there are only 3 points, Lagrange polynomial has degree 2. Explicitly,
+    it is given by
+
+    .. math::
+
+        \begin{aligned}
+            L(x) &= 1\times \frac{x (x - 2)}{-1} + 8\times \frac{x (x-1)}{2} \\
+                 &= x (-2 + 3x)
+        \end{aligned}
+
+    >>> from numpy.polynomial.polynomial import Polynomial
+    >>> Polynomial(poly.coef[::-1]).coef
+    array([ 0., -2.,  3.])
+
+    >>> import matplotlib.pyplot as plt
+    >>> x_new = np.arange(0, 2.1, 0.1)
+    >>> plt.scatter(x, y, label='data')
+    >>> plt.plot(x_new, Polynomial(poly.coef[::-1])(x_new), label='Polynomial')
+    >>> plt.plot(x_new, 3*x_new**2 - 2*x_new + 0*x_new,
+    ...          label=r"$3 x^2 - 2 x$", linestyle='-.')
+    >>> plt.legend()
+    >>> plt.show()
+
+    """
+
+    M = len(x)
+    p = poly1d(0.0)
+    for j in range(M):
+        pt = poly1d(w[j])
+        for k in range(M):
+            if k == j:
+                continue
+            fac = x[j]-x[k]
+            pt *= poly1d([1.0, -x[k]])/fac
+        p += pt
+    return p
+
+
+# !! Need to find argument for keeping initialize. If it isn't
+# !! found, get rid of it!
+
+
+dep_mesg = """\
+`interp2d` is deprecated in SciPy 1.10 and will be removed in SciPy 1.14.0.
+
+For legacy code, nearly bug-for-bug compatible replacements are
+`RectBivariateSpline` on regular grids, and `bisplrep`/`bisplev` for
+scattered 2D data.
+
+In new code, for regular grids use `RegularGridInterpolator` instead.
+For scattered data, prefer `LinearNDInterpolator` or
+`CloughTocher2DInterpolator`.
+
+For more details see
+`https://scipy.github.io/devdocs/notebooks/interp_transition_guide.html`
+"""
+
+class interp2d:
+    """
+    interp2d(x, y, z, kind='linear', copy=True, bounds_error=False,
+             fill_value=None)
+
+    .. deprecated:: 1.10.0
+
+        `interp2d` is deprecated in SciPy 1.10 and will be removed in SciPy
+        1.14.0.
+
+        For legacy code, nearly bug-for-bug compatible replacements are
+        `RectBivariateSpline` on regular grids, and `bisplrep`/`bisplev` for
+        scattered 2D data.
+
+        In new code, for regular grids use `RegularGridInterpolator` instead.
+        For scattered data, prefer `LinearNDInterpolator` or
+        `CloughTocher2DInterpolator`.
+
+        For more details see
+        `https://scipy.github.io/devdocs/notebooks/interp_transition_guide.html
+        <https://scipy.github.io/devdocs/notebooks/interp_transition_guide.html>`_
+
+
+    Interpolate over a 2-D grid.
+
+    `x`, `y` and `z` are arrays of values used to approximate some function
+    f: ``z = f(x, y)`` which returns a scalar value `z`. This class returns a
+    function whose call method uses spline interpolation to find the value
+    of new points.
+
+    If `x` and `y` represent a regular grid, consider using
+    `RectBivariateSpline`.
+
+    If `z` is a vector value, consider using `interpn`.
+
+    Note that calling `interp2d` with NaNs present in input values, or with
+    decreasing values in `x` an `y` results in undefined behaviour.
+
+    Methods
+    -------
+    __call__
+
+    Parameters
+    ----------
+    x, y : array_like
+        Arrays defining the data point coordinates.
+        The data point coordinates need to be sorted by increasing order.
+
+        If the points lie on a regular grid, `x` can specify the column
+        coordinates and `y` the row coordinates, for example::
+
+          >>> x = [0,1,2];  y = [0,3]; z = [[1,2,3], [4,5,6]]
+
+        Otherwise, `x` and `y` must specify the full coordinates for each
+        point, for example::
+
+          >>> x = [0,1,2,0,1,2];  y = [0,0,0,3,3,3]; z = [1,4,2,5,3,6]
+
+        If `x` and `y` are multidimensional, they are flattened before use.
+    z : array_like
+        The values of the function to interpolate at the data points. If
+        `z` is a multidimensional array, it is flattened before use assuming
+        Fortran-ordering (order='F').  The length of a flattened `z` array
+        is either len(`x`)*len(`y`) if `x` and `y` specify the column and
+        row coordinates or ``len(z) == len(x) == len(y)`` if `x` and `y`
+        specify coordinates for each point.
+    kind : {'linear', 'cubic', 'quintic'}, optional
+        The kind of spline interpolation to use. Default is 'linear'.
+    copy : bool, optional
+        If True, the class makes internal copies of x, y and z.
+        If False, references may be used. The default is to copy.
+    bounds_error : bool, optional
+        If True, when interpolated values are requested outside of the
+        domain of the input data (x,y), a ValueError is raised.
+        If False, then `fill_value` is used.
+    fill_value : number, optional
+        If provided, the value to use for points outside of the
+        interpolation domain. If omitted (None), values outside
+        the domain are extrapolated via nearest-neighbor extrapolation.
+
+    See Also
+    --------
+    RectBivariateSpline :
+        Much faster 2-D interpolation if your input data is on a grid
+    bisplrep, bisplev :
+        Spline interpolation based on FITPACK
+    BivariateSpline : a more recent wrapper of the FITPACK routines
+    interp1d : 1-D version of this function
+    RegularGridInterpolator : interpolation on a regular or rectilinear grid
+        in arbitrary dimensions.
+    interpn : Multidimensional interpolation on regular grids (wraps
+        `RegularGridInterpolator` and `RectBivariateSpline`).
+
+    Notes
+    -----
+    The minimum number of data points required along the interpolation
+    axis is ``(k+1)**2``, with k=1 for linear, k=3 for cubic and k=5 for
+    quintic interpolation.
+
+    The interpolator is constructed by `bisplrep`, with a smoothing factor
+    of 0. If more control over smoothing is needed, `bisplrep` should be
+    used directly.
+
+    The coordinates of the data points to interpolate `xnew` and `ynew`
+    have to be sorted by ascending order.
+    `interp2d` is legacy and is not
+    recommended for use in new code. New code should use
+    `RegularGridInterpolator` instead.
+
+    Examples
+    --------
+    Construct a 2-D grid and interpolate on it:
+
+    >>> import numpy as np
+    >>> from scipy import interpolate
+    >>> x = np.arange(-5.01, 5.01, 0.25)
+    >>> y = np.arange(-5.01, 5.01, 0.25)
+    >>> xx, yy = np.meshgrid(x, y)
+    >>> z = np.sin(xx**2+yy**2)
+    >>> f = interpolate.interp2d(x, y, z, kind='cubic')
+
+    Now use the obtained interpolation function and plot the result:
+
+    >>> import matplotlib.pyplot as plt
+    >>> xnew = np.arange(-5.01, 5.01, 1e-2)
+    >>> ynew = np.arange(-5.01, 5.01, 1e-2)
+    >>> znew = f(xnew, ynew)
+    >>> plt.plot(x, z[0, :], 'ro-', xnew, znew[0, :], 'b-')
+    >>> plt.show()
+    """
+
+    def __init__(self, x, y, z, kind='linear', copy=True, bounds_error=False,
+                 fill_value=None):
+        warnings.warn(dep_mesg, DeprecationWarning, stacklevel=2)
+
+        x = ravel(x)
+        y = ravel(y)
+        z = asarray(z)
+
+        rectangular_grid = (z.size == len(x) * len(y))
+        if rectangular_grid:
+            if z.ndim == 2:
+                if z.shape != (len(y), len(x)):
+                    raise ValueError("When on a regular grid with x.size = m "
+                                     "and y.size = n, if z.ndim == 2, then z "
+                                     "must have shape (n, m)")
+            if not np.all(x[1:] >= x[:-1]):
+                j = np.argsort(x)
+                x = x[j]
+                z = z[:, j]
+            if not np.all(y[1:] >= y[:-1]):
+                j = np.argsort(y)
+                y = y[j]
+                z = z[j, :]
+            z = ravel(z.T)
+        else:
+            z = ravel(z)
+            if len(x) != len(y):
+                raise ValueError(
+                    "x and y must have equal lengths for non rectangular grid")
+            if len(z) != len(x):
+                raise ValueError(
+                    "Invalid length for input z for non rectangular grid")
+
+        interpolation_types = {'linear': 1, 'cubic': 3, 'quintic': 5}
+        try:
+            kx = ky = interpolation_types[kind]
+        except KeyError as e:
+            raise ValueError(
+                f"Unsupported interpolation type {repr(kind)}, must be "
+                f"either of {', '.join(map(repr, interpolation_types))}."
+            ) from e
+
+        if not rectangular_grid:
+            # TODO: surfit is really not meant for interpolation!
+            self.tck = _fitpack_py.bisplrep(x, y, z, kx=kx, ky=ky, s=0.0)
+        else:
+            nx, tx, ny, ty, c, fp, ier = dfitpack.regrid_smth(
+                x, y, z, None, None, None, None,
+                kx=kx, ky=ky, s=0.0)
+            self.tck = (tx[:nx], ty[:ny], c[:(nx - kx - 1) * (ny - ky - 1)],
+                        kx, ky)
+
+        self.bounds_error = bounds_error
+        self.fill_value = fill_value
+        self.x, self.y, self.z = (array(a, copy=copy) for a in (x, y, z))
+
+        self.x_min, self.x_max = np.amin(x), np.amax(x)
+        self.y_min, self.y_max = np.amin(y), np.amax(y)
+
+    def __call__(self, x, y, dx=0, dy=0, assume_sorted=False):
+        """Interpolate the function.
+
+        Parameters
+        ----------
+        x : 1-D array
+            x-coordinates of the mesh on which to interpolate.
+        y : 1-D array
+            y-coordinates of the mesh on which to interpolate.
+        dx : int >= 0, < kx
+            Order of partial derivatives in x.
+        dy : int >= 0, < ky
+            Order of partial derivatives in y.
+        assume_sorted : bool, optional
+            If False, values of `x` and `y` can be in any order and they are
+            sorted first.
+            If True, `x` and `y` have to be arrays of monotonically
+            increasing values.
+
+        Returns
+        -------
+        z : 2-D array with shape (len(y), len(x))
+            The interpolated values.
+        """
+        warnings.warn(dep_mesg, DeprecationWarning, stacklevel=2)
+
+        x = atleast_1d(x)
+        y = atleast_1d(y)
+
+        if x.ndim != 1 or y.ndim != 1:
+            raise ValueError("x and y should both be 1-D arrays")
+
+        if not assume_sorted:
+            x = np.sort(x, kind="mergesort")
+            y = np.sort(y, kind="mergesort")
+
+        if self.bounds_error or self.fill_value is not None:
+            out_of_bounds_x = (x < self.x_min) | (x > self.x_max)
+            out_of_bounds_y = (y < self.y_min) | (y > self.y_max)
+
+            any_out_of_bounds_x = np.any(out_of_bounds_x)
+            any_out_of_bounds_y = np.any(out_of_bounds_y)
+
+        if self.bounds_error and (any_out_of_bounds_x or any_out_of_bounds_y):
+            raise ValueError(
+                f"Values out of range; x must be in {(self.x_min, self.x_max)!r}, "
+                f"y in {(self.y_min, self.y_max)!r}"
+            )
+
+        z = _fitpack_py.bisplev(x, y, self.tck, dx, dy)
+        z = atleast_2d(z)
+        z = transpose(z)
+
+        if self.fill_value is not None:
+            if any_out_of_bounds_x:
+                z[:, out_of_bounds_x] = self.fill_value
+            if any_out_of_bounds_y:
+                z[out_of_bounds_y, :] = self.fill_value
+
+        if len(z) == 1:
+            z = z[0]
+        return array(z)
+
+
+def _check_broadcast_up_to(arr_from, shape_to, name):
+    """Helper to check that arr_from broadcasts up to shape_to"""
+    shape_from = arr_from.shape
+    if len(shape_to) >= len(shape_from):
+        for t, f in zip(shape_to[::-1], shape_from[::-1]):
+            if f != 1 and f != t:
+                break
+        else:  # all checks pass, do the upcasting that we need later
+            if arr_from.size != 1 and arr_from.shape != shape_to:
+                arr_from = np.ones(shape_to, arr_from.dtype) * arr_from
+            return arr_from.ravel()
+    # at least one check failed
+    raise ValueError(f'{name} argument must be able to broadcast up '
+                     f'to shape {shape_to} but had shape {shape_from}')
+
+
+def _do_extrapolate(fill_value):
+    """Helper to check if fill_value == "extrapolate" without warnings"""
+    return (isinstance(fill_value, str) and
+            fill_value == 'extrapolate')
+
+
+class interp1d(_Interpolator1D):
+    """
+    Interpolate a 1-D function.
+
+    .. legacy:: class
+
+        For a guide to the intended replacements for `interp1d` see
+        :ref:`tutorial-interpolate_1Dsection`.
+
+    `x` and `y` are arrays of values used to approximate some function f:
+    ``y = f(x)``. This class returns a function whose call method uses
+    interpolation to find the value of new points.
+
+    Parameters
+    ----------
+    x : (npoints, ) array_like
+        A 1-D array of real values.
+    y : (..., npoints, ...) array_like
+        A N-D array of real values. The length of `y` along the interpolation
+        axis must be equal to the length of `x`. Use the ``axis`` parameter
+        to select correct axis. Unlike other interpolators, the default
+        interpolation axis is the last axis of `y`.
+    kind : str or int, optional
+        Specifies the kind of interpolation as a string or as an integer
+        specifying the order of the spline interpolator to use.
+        The string has to be one of 'linear', 'nearest', 'nearest-up', 'zero',
+        'slinear', 'quadratic', 'cubic', 'previous', or 'next'. 'zero',
+        'slinear', 'quadratic' and 'cubic' refer to a spline interpolation of
+        zeroth, first, second or third order; 'previous' and 'next' simply
+        return the previous or next value of the point; 'nearest-up' and
+        'nearest' differ when interpolating half-integers (e.g. 0.5, 1.5)
+        in that 'nearest-up' rounds up and 'nearest' rounds down. Default
+        is 'linear'.
+    axis : int, optional
+        Axis in the ``y`` array corresponding to the x-coordinate values. Unlike
+        other interpolators, defaults to ``axis=-1``.
+    copy : bool, optional
+        If ``True``, the class makes internal copies of x and y. If ``False``,
+        references to ``x`` and ``y`` are used if possible. The default is to copy.
+    bounds_error : bool, optional
+        If True, a ValueError is raised any time interpolation is attempted on
+        a value outside of the range of x (where extrapolation is
+        necessary). If False, out of bounds values are assigned `fill_value`.
+        By default, an error is raised unless ``fill_value="extrapolate"``.
+    fill_value : array-like or (array-like, array_like) or "extrapolate", optional
+        - if a ndarray (or float), this value will be used to fill in for
+          requested points outside of the data range. If not provided, then
+          the default is NaN. The array-like must broadcast properly to the
+          dimensions of the non-interpolation axes.
+        - If a two-element tuple, then the first element is used as a
+          fill value for ``x_new < x[0]`` and the second element is used for
+          ``x_new > x[-1]``. Anything that is not a 2-element tuple (e.g.,
+          list or ndarray, regardless of shape) is taken to be a single
+          array-like argument meant to be used for both bounds as
+          ``below, above = fill_value, fill_value``. Using a two-element tuple
+          or ndarray requires ``bounds_error=False``.
+
+          .. versionadded:: 0.17.0
+        - If "extrapolate", then points outside the data range will be
+          extrapolated.
+
+          .. versionadded:: 0.17.0
+    assume_sorted : bool, optional
+        If False, values of `x` can be in any order and they are sorted first.
+        If True, `x` has to be an array of monotonically increasing values.
+
+    Attributes
+    ----------
+    fill_value
+
+    Methods
+    -------
+    __call__
+
+    See Also
+    --------
+    splrep, splev
+        Spline interpolation/smoothing based on FITPACK.
+    UnivariateSpline : An object-oriented wrapper of the FITPACK routines.
+    interp2d : 2-D interpolation
+
+    Notes
+    -----
+    Calling `interp1d` with NaNs present in input values results in
+    undefined behaviour.
+
+    Input values `x` and `y` must be convertible to `float` values like
+    `int` or `float`.
+
+    If the values in `x` are not unique, the resulting behavior is
+    undefined and specific to the choice of `kind`, i.e., changing
+    `kind` will change the behavior for duplicates.
+
+
+    Examples
+    --------
+    >>> import numpy as np
+    >>> import matplotlib.pyplot as plt
+    >>> from scipy import interpolate
+    >>> x = np.arange(0, 10)
+    >>> y = np.exp(-x/3.0)
+    >>> f = interpolate.interp1d(x, y)
+
+    >>> xnew = np.arange(0, 9, 0.1)
+    >>> ynew = f(xnew)   # use interpolation function returned by `interp1d`
+    >>> plt.plot(x, y, 'o', xnew, ynew, '-')
+    >>> plt.show()
+    """
+
+    def __init__(self, x, y, kind='linear', axis=-1,
+                 copy=True, bounds_error=None, fill_value=np.nan,
+                 assume_sorted=False):
+        """ Initialize a 1-D linear interpolation class."""
+        _Interpolator1D.__init__(self, x, y, axis=axis)
+
+        self.bounds_error = bounds_error  # used by fill_value setter
+
+        # `copy` keyword semantics changed in NumPy 2.0, once that is
+        # the minimum version this can use `copy=None`.
+        self.copy = copy
+        if not copy:
+            self.copy = copy_if_needed
+
+        if kind in ['zero', 'slinear', 'quadratic', 'cubic']:
+            order = {'zero': 0, 'slinear': 1,
+                     'quadratic': 2, 'cubic': 3}[kind]
+            kind = 'spline'
+        elif isinstance(kind, int):
+            order = kind
+            kind = 'spline'
+        elif kind not in ('linear', 'nearest', 'nearest-up', 'previous',
+                          'next'):
+            raise NotImplementedError("%s is unsupported: Use fitpack "
+                                      "routines for other types." % kind)
+        x = array(x, copy=self.copy)
+        y = array(y, copy=self.copy)
+
+        if not assume_sorted:
+            ind = np.argsort(x, kind="mergesort")
+            x = x[ind]
+            y = np.take(y, ind, axis=axis)
+
+        if x.ndim != 1:
+            raise ValueError("the x array must have exactly one dimension.")
+        if y.ndim == 0:
+            raise ValueError("the y array must have at least one dimension.")
+
+        # Force-cast y to a floating-point type, if it's not yet one
+        if not issubclass(y.dtype.type, np.inexact):
+            y = y.astype(np.float64)
+
+        # Backward compatibility
+        self.axis = axis % y.ndim
+
+        # Interpolation goes internally along the first axis
+        self.y = y
+        self._y = self._reshape_yi(self.y)
+        self.x = x
+        del y, x  # clean up namespace to prevent misuse; use attributes
+        self._kind = kind
+
+        # Adjust to interpolation kind; store reference to *unbound*
+        # interpolation methods, in order to avoid circular references to self
+        # stored in the bound instance methods, and therefore delayed garbage
+        # collection.  See: https://docs.python.org/reference/datamodel.html
+        if kind in ('linear', 'nearest', 'nearest-up', 'previous', 'next'):
+            # Make a "view" of the y array that is rotated to the interpolation
+            # axis.
+            minval = 1
+            if kind == 'nearest':
+                # Do division before addition to prevent possible integer
+                # overflow
+                self._side = 'left'
+                self.x_bds = self.x / 2.0
+                self.x_bds = self.x_bds[1:] + self.x_bds[:-1]
+
+                self._call = self.__class__._call_nearest
+            elif kind == 'nearest-up':
+                # Do division before addition to prevent possible integer
+                # overflow
+                self._side = 'right'
+                self.x_bds = self.x / 2.0
+                self.x_bds = self.x_bds[1:] + self.x_bds[:-1]
+
+                self._call = self.__class__._call_nearest
+            elif kind == 'previous':
+                # Side for np.searchsorted and index for clipping
+                self._side = 'left'
+                self._ind = 0
+                # Move x by one floating point value to the left
+                self._x_shift = np.nextafter(self.x, -np.inf)
+                self._call = self.__class__._call_previousnext
+                if _do_extrapolate(fill_value):
+                    self._check_and_update_bounds_error_for_extrapolation()
+                    # assume y is sorted by x ascending order here.
+                    fill_value = (np.nan, np.take(self.y, -1, axis))
+            elif kind == 'next':
+                self._side = 'right'
+                self._ind = 1
+                # Move x by one floating point value to the right
+                self._x_shift = np.nextafter(self.x, np.inf)
+                self._call = self.__class__._call_previousnext
+                if _do_extrapolate(fill_value):
+                    self._check_and_update_bounds_error_for_extrapolation()
+                    # assume y is sorted by x ascending order here.
+                    fill_value = (np.take(self.y, 0, axis), np.nan)
+            else:
+                # Check if we can delegate to numpy.interp (2x-10x faster).
+                np_dtypes = (np.dtype(np.float64), np.dtype(int))
+                cond = self.x.dtype in np_dtypes and self.y.dtype in np_dtypes
+                cond = cond and self.y.ndim == 1
+                cond = cond and not _do_extrapolate(fill_value)
+
+                if cond:
+                    self._call = self.__class__._call_linear_np
+                else:
+                    self._call = self.__class__._call_linear
+        else:
+            minval = order + 1
+
+            rewrite_nan = False
+            xx, yy = self.x, self._y
+            if order > 1:
+                # Quadratic or cubic spline. If input contains even a single
+                # nan, then the output is all nans. We cannot just feed data
+                # with nans to make_interp_spline because it calls LAPACK.
+                # So, we make up a bogus x and y with no nans and use it
+                # to get the correct shape of the output, which we then fill
+                # with nans.
+                # For slinear or zero order spline, we just pass nans through.
+                mask = np.isnan(self.x)
+                if mask.any():
+                    sx = self.x[~mask]
+                    if sx.size == 0:
+                        raise ValueError("`x` array is all-nan")
+                    xx = np.linspace(np.nanmin(self.x),
+                                     np.nanmax(self.x),
+                                     len(self.x))
+                    rewrite_nan = True
+                if np.isnan(self._y).any():
+                    yy = np.ones_like(self._y)
+                    rewrite_nan = True
+
+            self._spline = make_interp_spline(xx, yy, k=order,
+                                              check_finite=False)
+            if rewrite_nan:
+                self._call = self.__class__._call_nan_spline
+            else:
+                self._call = self.__class__._call_spline
+
+        if len(self.x) < minval:
+            raise ValueError("x and y arrays must have at "
+                             "least %d entries" % minval)
+
+        self.fill_value = fill_value  # calls the setter, can modify bounds_err
+
+    @property
+    def fill_value(self):
+        """The fill value."""
+        # backwards compat: mimic a public attribute
+        return self._fill_value_orig
+
+    @fill_value.setter
+    def fill_value(self, fill_value):
+        # extrapolation only works for nearest neighbor and linear methods
+        if _do_extrapolate(fill_value):
+            self._check_and_update_bounds_error_for_extrapolation()
+            self._extrapolate = True
+        else:
+            broadcast_shape = (self.y.shape[:self.axis] +
+                               self.y.shape[self.axis + 1:])
+            if len(broadcast_shape) == 0:
+                broadcast_shape = (1,)
+            # it's either a pair (_below_range, _above_range) or a single value
+            # for both above and below range
+            if isinstance(fill_value, tuple) and len(fill_value) == 2:
+                below_above = [np.asarray(fill_value[0]),
+                               np.asarray(fill_value[1])]
+                names = ('fill_value (below)', 'fill_value (above)')
+                for ii in range(2):
+                    below_above[ii] = _check_broadcast_up_to(
+                        below_above[ii], broadcast_shape, names[ii])
+            else:
+                fill_value = np.asarray(fill_value)
+                below_above = [_check_broadcast_up_to(
+                    fill_value, broadcast_shape, 'fill_value')] * 2
+            self._fill_value_below, self._fill_value_above = below_above
+            self._extrapolate = False
+            if self.bounds_error is None:
+                self.bounds_error = True
+        # backwards compat: fill_value was a public attr; make it writeable
+        self._fill_value_orig = fill_value
+
+    def _check_and_update_bounds_error_for_extrapolation(self):
+        if self.bounds_error:
+            raise ValueError("Cannot extrapolate and raise "
+                             "at the same time.")
+        self.bounds_error = False
+
+    def _call_linear_np(self, x_new):
+        # Note that out-of-bounds values are taken care of in self._evaluate
+        return np.interp(x_new, self.x, self.y)
+
+    def _call_linear(self, x_new):
+        # 2. Find where in the original data, the values to interpolate
+        #    would be inserted.
+        #    Note: If x_new[n] == x[m], then m is returned by searchsorted.
+        x_new_indices = searchsorted(self.x, x_new)
+
+        # 3. Clip x_new_indices so that they are within the range of
+        #    self.x indices and at least 1. Removes mis-interpolation
+        #    of x_new[n] = x[0]
+        x_new_indices = x_new_indices.clip(1, len(self.x)-1).astype(int)
+
+        # 4. Calculate the slope of regions that each x_new value falls in.
+        lo = x_new_indices - 1
+        hi = x_new_indices
+
+        x_lo = self.x[lo]
+        x_hi = self.x[hi]
+        y_lo = self._y[lo]
+        y_hi = self._y[hi]
+
+        # Note that the following two expressions rely on the specifics of the
+        # broadcasting semantics.
+        slope = (y_hi - y_lo) / (x_hi - x_lo)[:, None]
+
+        # 5. Calculate the actual value for each entry in x_new.
+        y_new = slope*(x_new - x_lo)[:, None] + y_lo
+
+        return y_new
+
+    def _call_nearest(self, x_new):
+        """ Find nearest neighbor interpolated y_new = f(x_new)."""
+
+        # 2. Find where in the averaged data the values to interpolate
+        #    would be inserted.
+        #    Note: use side='left' (right) to searchsorted() to define the
+        #    halfway point to be nearest to the left (right) neighbor
+        x_new_indices = searchsorted(self.x_bds, x_new, side=self._side)
+
+        # 3. Clip x_new_indices so that they are within the range of x indices.
+        x_new_indices = x_new_indices.clip(0, len(self.x)-1).astype(intp)
+
+        # 4. Calculate the actual value for each entry in x_new.
+        y_new = self._y[x_new_indices]
+
+        return y_new
+
+    def _call_previousnext(self, x_new):
+        """Use previous/next neighbor of x_new, y_new = f(x_new)."""
+
+        # 1. Get index of left/right value
+        x_new_indices = searchsorted(self._x_shift, x_new, side=self._side)
+
+        # 2. Clip x_new_indices so that they are within the range of x indices.
+        x_new_indices = x_new_indices.clip(1-self._ind,
+                                           len(self.x)-self._ind).astype(intp)
+
+        # 3. Calculate the actual value for each entry in x_new.
+        y_new = self._y[x_new_indices+self._ind-1]
+
+        return y_new
+
+    def _call_spline(self, x_new):
+        return self._spline(x_new)
+
+    def _call_nan_spline(self, x_new):
+        out = self._spline(x_new)
+        out[...] = np.nan
+        return out
+
+    def _evaluate(self, x_new):
+        # 1. Handle values in x_new that are outside of x. Throw error,
+        #    or return a list of mask array indicating the outofbounds values.
+        #    The behavior is set by the bounds_error variable.
+        x_new = asarray(x_new)
+        y_new = self._call(self, x_new)
+        if not self._extrapolate:
+            below_bounds, above_bounds = self._check_bounds(x_new)
+            if len(y_new) > 0:
+                # Note fill_value must be broadcast up to the proper size
+                # and flattened to work here
+                y_new[below_bounds] = self._fill_value_below
+                y_new[above_bounds] = self._fill_value_above
+        return y_new
+
+    def _check_bounds(self, x_new):
+        """Check the inputs for being in the bounds of the interpolated data.
+
+        Parameters
+        ----------
+        x_new : array
+
+        Returns
+        -------
+        out_of_bounds : bool array
+            The mask on x_new of values that are out of the bounds.
+        """
+
+        # If self.bounds_error is True, we raise an error if any x_new values
+        # fall outside the range of x. Otherwise, we return an array indicating
+        # which values are outside the boundary region.
+        below_bounds = x_new < self.x[0]
+        above_bounds = x_new > self.x[-1]
+
+        if self.bounds_error and below_bounds.any():
+            below_bounds_value = x_new[np.argmax(below_bounds)]
+            raise ValueError(f"A value ({below_bounds_value}) in x_new is below "
+                             f"the interpolation range's minimum value ({self.x[0]}).")
+        if self.bounds_error and above_bounds.any():
+            above_bounds_value = x_new[np.argmax(above_bounds)]
+            raise ValueError(f"A value ({above_bounds_value}) in x_new is above "
+                             f"the interpolation range's maximum value ({self.x[-1]}).")
+
+        # !! Should we emit a warning if some values are out of bounds?
+        # !! matlab does not.
+        return below_bounds, above_bounds
+
+
+class _PPolyBase:
+    """Base class for piecewise polynomials."""
+    __slots__ = ('c', 'x', 'extrapolate', 'axis')
+
+    def __init__(self, c, x, extrapolate=None, axis=0):
+        self.c = np.asarray(c)
+        self.x = np.ascontiguousarray(x, dtype=np.float64)
+
+        if extrapolate is None:
+            extrapolate = True
+        elif extrapolate != 'periodic':
+            extrapolate = bool(extrapolate)
+        self.extrapolate = extrapolate
+
+        if self.c.ndim < 2:
+            raise ValueError("Coefficients array must be at least "
+                             "2-dimensional.")
+
+        if not (0 <= axis < self.c.ndim - 1):
+            raise ValueError(f"axis={axis} must be between 0 and {self.c.ndim-1}")
+
+        self.axis = axis
+        if axis != 0:
+            # move the interpolation axis to be the first one in self.c
+            # More specifically, the target shape for self.c is (k, m, ...),
+            # and axis !=0 means that we have c.shape (..., k, m, ...)
+            #                                               ^
+            #                                              axis
+            # So we roll two of them.
+            self.c = np.moveaxis(self.c, axis+1, 0)
+            self.c = np.moveaxis(self.c, axis+1, 0)
+
+        if self.x.ndim != 1:
+            raise ValueError("x must be 1-dimensional")
+        if self.x.size < 2:
+            raise ValueError("at least 2 breakpoints are needed")
+        if self.c.ndim < 2:
+            raise ValueError("c must have at least 2 dimensions")
+        if self.c.shape[0] == 0:
+            raise ValueError("polynomial must be at least of order 0")
+        if self.c.shape[1] != self.x.size-1:
+            raise ValueError("number of coefficients != len(x)-1")
+        dx = np.diff(self.x)
+        if not (np.all(dx >= 0) or np.all(dx <= 0)):
+            raise ValueError("`x` must be strictly increasing or decreasing.")
+
+        dtype = self._get_dtype(self.c.dtype)
+        self.c = np.ascontiguousarray(self.c, dtype=dtype)
+
+    def _get_dtype(self, dtype):
+        if np.issubdtype(dtype, np.complexfloating) \
+               or np.issubdtype(self.c.dtype, np.complexfloating):
+            return np.complex128
+        else:
+            return np.float64
+
+    @classmethod
+    def construct_fast(cls, c, x, extrapolate=None, axis=0):
+        """
+        Construct the piecewise polynomial without making checks.
+
+        Takes the same parameters as the constructor. Input arguments
+        ``c`` and ``x`` must be arrays of the correct shape and type. The
+        ``c`` array can only be of dtypes float and complex, and ``x``
+        array must have dtype float.
+        """
+        self = object.__new__(cls)
+        self.c = c
+        self.x = x
+        self.axis = axis
+        if extrapolate is None:
+            extrapolate = True
+        self.extrapolate = extrapolate
+        return self
+
+    def _ensure_c_contiguous(self):
+        """
+        c and x may be modified by the user. The Cython code expects
+        that they are C contiguous.
+        """
+        if not self.x.flags.c_contiguous:
+            self.x = self.x.copy()
+        if not self.c.flags.c_contiguous:
+            self.c = self.c.copy()
+
+    def extend(self, c, x):
+        """
+        Add additional breakpoints and coefficients to the polynomial.
+
+        Parameters
+        ----------
+        c : ndarray, size (k, m, ...)
+            Additional coefficients for polynomials in intervals. Note that
+            the first additional interval will be formed using one of the
+            ``self.x`` end points.
+        x : ndarray, size (m,)
+            Additional breakpoints. Must be sorted in the same order as
+            ``self.x`` and either to the right or to the left of the current
+            breakpoints.
+        """
+
+        c = np.asarray(c)
+        x = np.asarray(x)
+
+        if c.ndim < 2:
+            raise ValueError("invalid dimensions for c")
+        if x.ndim != 1:
+            raise ValueError("invalid dimensions for x")
+        if x.shape[0] != c.shape[1]:
+            raise ValueError(f"Shapes of x {x.shape} and c {c.shape} are incompatible")
+        if c.shape[2:] != self.c.shape[2:] or c.ndim != self.c.ndim:
+            raise ValueError("Shapes of c {} and self.c {} are incompatible"
+                             .format(c.shape, self.c.shape))
+
+        if c.size == 0:
+            return
+
+        dx = np.diff(x)
+        if not (np.all(dx >= 0) or np.all(dx <= 0)):
+            raise ValueError("`x` is not sorted.")
+
+        if self.x[-1] >= self.x[0]:
+            if not x[-1] >= x[0]:
+                raise ValueError("`x` is in the different order "
+                                 "than `self.x`.")
+
+            if x[0] >= self.x[-1]:
+                action = 'append'
+            elif x[-1] <= self.x[0]:
+                action = 'prepend'
+            else:
+                raise ValueError("`x` is neither on the left or on the right "
+                                 "from `self.x`.")
+        else:
+            if not x[-1] <= x[0]:
+                raise ValueError("`x` is in the different order "
+                                 "than `self.x`.")
+
+            if x[0] <= self.x[-1]:
+                action = 'append'
+            elif x[-1] >= self.x[0]:
+                action = 'prepend'
+            else:
+                raise ValueError("`x` is neither on the left or on the right "
+                                 "from `self.x`.")
+
+        dtype = self._get_dtype(c.dtype)
+
+        k2 = max(c.shape[0], self.c.shape[0])
+        c2 = np.zeros((k2, self.c.shape[1] + c.shape[1]) + self.c.shape[2:],
+                      dtype=dtype)
+
+        if action == 'append':
+            c2[k2-self.c.shape[0]:, :self.c.shape[1]] = self.c
+            c2[k2-c.shape[0]:, self.c.shape[1]:] = c
+            self.x = np.r_[self.x, x]
+        elif action == 'prepend':
+            c2[k2-self.c.shape[0]:, :c.shape[1]] = c
+            c2[k2-c.shape[0]:, c.shape[1]:] = self.c
+            self.x = np.r_[x, self.x]
+
+        self.c = c2
+
+    def __call__(self, x, nu=0, extrapolate=None):
+        """
+        Evaluate the piecewise polynomial or its derivative.
+
+        Parameters
+        ----------
+        x : array_like
+            Points to evaluate the interpolant at.
+        nu : int, optional
+            Order of derivative to evaluate. Must be non-negative.
+        extrapolate : {bool, 'periodic', None}, optional
+            If bool, determines whether to extrapolate to out-of-bounds points
+            based on first and last intervals, or to return NaNs.
+            If 'periodic', periodic extrapolation is used.
+            If None (default), use `self.extrapolate`.
+
+        Returns
+        -------
+        y : array_like
+            Interpolated values. Shape is determined by replacing
+            the interpolation axis in the original array with the shape of x.
+
+        Notes
+        -----
+        Derivatives are evaluated piecewise for each polynomial
+        segment, even if the polynomial is not differentiable at the
+        breakpoints. The polynomial intervals are considered half-open,
+        ``[a, b)``, except for the last interval which is closed
+        ``[a, b]``.
+        """
+        if extrapolate is None:
+            extrapolate = self.extrapolate
+        x = np.asarray(x)
+        x_shape, x_ndim = x.shape, x.ndim
+        x = np.ascontiguousarray(x.ravel(), dtype=np.float64)
+
+        # With periodic extrapolation we map x to the segment
+        # [self.x[0], self.x[-1]].
+        if extrapolate == 'periodic':
+            x = self.x[0] + (x - self.x[0]) % (self.x[-1] - self.x[0])
+            extrapolate = False
+
+        out = np.empty((len(x), prod(self.c.shape[2:])), dtype=self.c.dtype)
+        self._ensure_c_contiguous()
+        self._evaluate(x, nu, extrapolate, out)
+        out = out.reshape(x_shape + self.c.shape[2:])
+        if self.axis != 0:
+            # transpose to move the calculated values to the interpolation axis
+            l = list(range(out.ndim))
+            l = l[x_ndim:x_ndim+self.axis] + l[:x_ndim] + l[x_ndim+self.axis:]
+            out = out.transpose(l)
+        return out
+
+
+class PPoly(_PPolyBase):
+    """
+    Piecewise polynomial in terms of coefficients and breakpoints
+
+    The polynomial between ``x[i]`` and ``x[i + 1]`` is written in the
+    local power basis::
+
+        S = sum(c[m, i] * (xp - x[i])**(k-m) for m in range(k+1))
+
+    where ``k`` is the degree of the polynomial.
+
+    Parameters
+    ----------
+    c : ndarray, shape (k, m, ...)
+        Polynomial coefficients, order `k` and `m` intervals.
+    x : ndarray, shape (m+1,)
+        Polynomial breakpoints. Must be sorted in either increasing or
+        decreasing order.
+    extrapolate : bool or 'periodic', optional
+        If bool, determines whether to extrapolate to out-of-bounds points
+        based on first and last intervals, or to return NaNs. If 'periodic',
+        periodic extrapolation is used. Default is True.
+    axis : int, optional
+        Interpolation axis. Default is zero.
+
+    Attributes
+    ----------
+    x : ndarray
+        Breakpoints.
+    c : ndarray
+        Coefficients of the polynomials. They are reshaped
+        to a 3-D array with the last dimension representing
+        the trailing dimensions of the original coefficient array.
+    axis : int
+        Interpolation axis.
+
+    Methods
+    -------
+    __call__
+    derivative
+    antiderivative
+    integrate
+    solve
+    roots
+    extend
+    from_spline
+    from_bernstein_basis
+    construct_fast
+
+    See also
+    --------
+    BPoly : piecewise polynomials in the Bernstein basis
+
+    Notes
+    -----
+    High-order polynomials in the power basis can be numerically
+    unstable. Precision problems can start to appear for orders
+    larger than 20-30.
+    """
+
+    def _evaluate(self, x, nu, extrapolate, out):
+        _ppoly.evaluate(self.c.reshape(self.c.shape[0], self.c.shape[1], -1),
+                        self.x, x, nu, bool(extrapolate), out)
+
+    def derivative(self, nu=1):
+        """
+        Construct a new piecewise polynomial representing the derivative.
+
+        Parameters
+        ----------
+        nu : int, optional
+            Order of derivative to evaluate. Default is 1, i.e., compute the
+            first derivative. If negative, the antiderivative is returned.
+
+        Returns
+        -------
+        pp : PPoly
+            Piecewise polynomial of order k2 = k - n representing the derivative
+            of this polynomial.
+
+        Notes
+        -----
+        Derivatives are evaluated piecewise for each polynomial
+        segment, even if the polynomial is not differentiable at the
+        breakpoints. The polynomial intervals are considered half-open,
+        ``[a, b)``, except for the last interval which is closed
+        ``[a, b]``.
+        """
+        if nu < 0:
+            return self.antiderivative(-nu)
+
+        # reduce order
+        if nu == 0:
+            c2 = self.c.copy()
+        else:
+            c2 = self.c[:-nu, :].copy()
+
+        if c2.shape[0] == 0:
+            # derivative of order 0 is zero
+            c2 = np.zeros((1,) + c2.shape[1:], dtype=c2.dtype)
+
+        # multiply by the correct rising factorials
+        factor = spec.poch(np.arange(c2.shape[0], 0, -1), nu)
+        c2 *= factor[(slice(None),) + (None,)*(c2.ndim-1)]
+
+        # construct a compatible polynomial
+        return self.construct_fast(c2, self.x, self.extrapolate, self.axis)
+
+    def antiderivative(self, nu=1):
+        """
+        Construct a new piecewise polynomial representing the antiderivative.
+
+        Antiderivative is also the indefinite integral of the function,
+        and derivative is its inverse operation.
+
+        Parameters
+        ----------
+        nu : int, optional
+            Order of antiderivative to evaluate. Default is 1, i.e., compute
+            the first integral. If negative, the derivative is returned.
+
+        Returns
+        -------
+        pp : PPoly
+            Piecewise polynomial of order k2 = k + n representing
+            the antiderivative of this polynomial.
+
+        Notes
+        -----
+        The antiderivative returned by this function is continuous and
+        continuously differentiable to order n-1, up to floating point
+        rounding error.
+
+        If antiderivative is computed and ``self.extrapolate='periodic'``,
+        it will be set to False for the returned instance. This is done because
+        the antiderivative is no longer periodic and its correct evaluation
+        outside of the initially given x interval is difficult.
+        """
+        if nu <= 0:
+            return self.derivative(-nu)
+
+        c = np.zeros((self.c.shape[0] + nu, self.c.shape[1]) + self.c.shape[2:],
+                     dtype=self.c.dtype)
+        c[:-nu] = self.c
+
+        # divide by the correct rising factorials
+        factor = spec.poch(np.arange(self.c.shape[0], 0, -1), nu)
+        c[:-nu] /= factor[(slice(None),) + (None,)*(c.ndim-1)]
+
+        # fix continuity of added degrees of freedom
+        self._ensure_c_contiguous()
+        _ppoly.fix_continuity(c.reshape(c.shape[0], c.shape[1], -1),
+                              self.x, nu - 1)
+
+        if self.extrapolate == 'periodic':
+            extrapolate = False
+        else:
+            extrapolate = self.extrapolate
+
+        # construct a compatible polynomial
+        return self.construct_fast(c, self.x, extrapolate, self.axis)
+
+    def integrate(self, a, b, extrapolate=None):
+        """
+        Compute a definite integral over a piecewise polynomial.
+
+        Parameters
+        ----------
+        a : float
+            Lower integration bound
+        b : float
+            Upper integration bound
+        extrapolate : {bool, 'periodic', None}, optional
+            If bool, determines whether to extrapolate to out-of-bounds points
+            based on first and last intervals, or to return NaNs.
+            If 'periodic', periodic extrapolation is used.
+            If None (default), use `self.extrapolate`.
+
+        Returns
+        -------
+        ig : array_like
+            Definite integral of the piecewise polynomial over [a, b]
+        """
+        if extrapolate is None:
+            extrapolate = self.extrapolate
+
+        # Swap integration bounds if needed
+        sign = 1
+        if b < a:
+            a, b = b, a
+            sign = -1
+
+        range_int = np.empty((prod(self.c.shape[2:]),), dtype=self.c.dtype)
+        self._ensure_c_contiguous()
+
+        # Compute the integral.
+        if extrapolate == 'periodic':
+            # Split the integral into the part over period (can be several
+            # of them) and the remaining part.
+
+            xs, xe = self.x[0], self.x[-1]
+            period = xe - xs
+            interval = b - a
+            n_periods, left = divmod(interval, period)
+
+            if n_periods > 0:
+                _ppoly.integrate(
+                    self.c.reshape(self.c.shape[0], self.c.shape[1], -1),
+                    self.x, xs, xe, False, out=range_int)
+                range_int *= n_periods
+            else:
+                range_int.fill(0)
+
+            # Map a to [xs, xe], b is always a + left.
+            a = xs + (a - xs) % period
+            b = a + left
+
+            # If b <= xe then we need to integrate over [a, b], otherwise
+            # over [a, xe] and from xs to what is remained.
+            remainder_int = np.empty_like(range_int)
+            if b <= xe:
+                _ppoly.integrate(
+                    self.c.reshape(self.c.shape[0], self.c.shape[1], -1),
+                    self.x, a, b, False, out=remainder_int)
+                range_int += remainder_int
+            else:
+                _ppoly.integrate(
+                    self.c.reshape(self.c.shape[0], self.c.shape[1], -1),
+                    self.x, a, xe, False, out=remainder_int)
+                range_int += remainder_int
+
+                _ppoly.integrate(
+                    self.c.reshape(self.c.shape[0], self.c.shape[1], -1),
+                    self.x, xs, xs + left + a - xe, False, out=remainder_int)
+                range_int += remainder_int
+        else:
+            _ppoly.integrate(
+                self.c.reshape(self.c.shape[0], self.c.shape[1], -1),
+                self.x, a, b, bool(extrapolate), out=range_int)
+
+        # Return
+        range_int *= sign
+        return range_int.reshape(self.c.shape[2:])
+
+    def solve(self, y=0., discontinuity=True, extrapolate=None):
+        """
+        Find real solutions of the equation ``pp(x) == y``.
+
+        Parameters
+        ----------
+        y : float, optional
+            Right-hand side. Default is zero.
+        discontinuity : bool, optional
+            Whether to report sign changes across discontinuities at
+            breakpoints as roots.
+        extrapolate : {bool, 'periodic', None}, optional
+            If bool, determines whether to return roots from the polynomial
+            extrapolated based on first and last intervals, 'periodic' works
+            the same as False. If None (default), use `self.extrapolate`.
+
+        Returns
+        -------
+        roots : ndarray
+            Roots of the polynomial(s).
+
+            If the PPoly object describes multiple polynomials, the
+            return value is an object array whose each element is an
+            ndarray containing the roots.
+
+        Notes
+        -----
+        This routine works only on real-valued polynomials.
+
+        If the piecewise polynomial contains sections that are
+        identically zero, the root list will contain the start point
+        of the corresponding interval, followed by a ``nan`` value.
+
+        If the polynomial is discontinuous across a breakpoint, and
+        there is a sign change across the breakpoint, this is reported
+        if the `discont` parameter is True.
+
+        Examples
+        --------
+
+        Finding roots of ``[x**2 - 1, (x - 1)**2]`` defined on intervals
+        ``[-2, 1], [1, 2]``:
+
+        >>> import numpy as np
+        >>> from scipy.interpolate import PPoly
+        >>> pp = PPoly(np.array([[1, -4, 3], [1, 0, 0]]).T, [-2, 1, 2])
+        >>> pp.solve()
+        array([-1.,  1.])
+        """
+        if extrapolate is None:
+            extrapolate = self.extrapolate
+
+        self._ensure_c_contiguous()
+
+        if np.issubdtype(self.c.dtype, np.complexfloating):
+            raise ValueError("Root finding is only for "
+                             "real-valued polynomials")
+
+        y = float(y)
+        r = _ppoly.real_roots(self.c.reshape(self.c.shape[0], self.c.shape[1], -1),
+                              self.x, y, bool(discontinuity),
+                              bool(extrapolate))
+        if self.c.ndim == 2:
+            return r[0]
+        else:
+            r2 = np.empty(prod(self.c.shape[2:]), dtype=object)
+            # this for-loop is equivalent to ``r2[...] = r``, but that's broken
+            # in NumPy 1.6.0
+            for ii, root in enumerate(r):
+                r2[ii] = root
+
+            return r2.reshape(self.c.shape[2:])
+
+    def roots(self, discontinuity=True, extrapolate=None):
+        """
+        Find real roots of the piecewise polynomial.
+
+        Parameters
+        ----------
+        discontinuity : bool, optional
+            Whether to report sign changes across discontinuities at
+            breakpoints as roots.
+        extrapolate : {bool, 'periodic', None}, optional
+            If bool, determines whether to return roots from the polynomial
+            extrapolated based on first and last intervals, 'periodic' works
+            the same as False. If None (default), use `self.extrapolate`.
+
+        Returns
+        -------
+        roots : ndarray
+            Roots of the polynomial(s).
+
+            If the PPoly object describes multiple polynomials, the
+            return value is an object array whose each element is an
+            ndarray containing the roots.
+
+        See Also
+        --------
+        PPoly.solve
+        """
+        return self.solve(0, discontinuity, extrapolate)
+
+    @classmethod
+    def from_spline(cls, tck, extrapolate=None):
+        """
+        Construct a piecewise polynomial from a spline
+
+        Parameters
+        ----------
+        tck
+            A spline, as returned by `splrep` or a BSpline object.
+        extrapolate : bool or 'periodic', optional
+            If bool, determines whether to extrapolate to out-of-bounds points
+            based on first and last intervals, or to return NaNs.
+            If 'periodic', periodic extrapolation is used. Default is True.
+
+        Examples
+        --------
+        Construct an interpolating spline and convert it to a `PPoly` instance 
+
+        >>> import numpy as np
+        >>> from scipy.interpolate import splrep, PPoly
+        >>> x = np.linspace(0, 1, 11)
+        >>> y = np.sin(2*np.pi*x)
+        >>> tck = splrep(x, y, s=0)
+        >>> p = PPoly.from_spline(tck)
+        >>> isinstance(p, PPoly)
+        True
+
+        Note that this function only supports 1D splines out of the box.
+
+        If the ``tck`` object represents a parametric spline (e.g. constructed
+        by `splprep` or a `BSpline` with ``c.ndim > 1``), you will need to loop
+        over the dimensions manually.
+
+        >>> from scipy.interpolate import splprep, splev
+        >>> t = np.linspace(0, 1, 11)
+        >>> x = np.sin(2*np.pi*t)
+        >>> y = np.cos(2*np.pi*t)
+        >>> (t, c, k), u = splprep([x, y], s=0)
+
+        Note that ``c`` is a list of two arrays of length 11.
+
+        >>> unew = np.arange(0, 1.01, 0.01)
+        >>> out = splev(unew, (t, c, k))
+
+        To convert this spline to the power basis, we convert each
+        component of the list of b-spline coefficients, ``c``, into the
+        corresponding cubic polynomial.
+
+        >>> polys = [PPoly.from_spline((t, cj, k)) for cj in c]
+        >>> polys[0].c.shape
+        (4, 14)
+
+        Note that the coefficients of the polynomials `polys` are in the
+        power basis and their dimensions reflect just that: here 4 is the order
+        (degree+1), and 14 is the number of intervals---which is nothing but
+        the length of the knot array of the original `tck` minus one.
+
+        Optionally, we can stack the components into a single `PPoly` along
+        the third dimension:
+
+        >>> cc = np.dstack([p.c for p in polys])    # has shape = (4, 14, 2)
+        >>> poly = PPoly(cc, polys[0].x)
+        >>> np.allclose(poly(unew).T,     # note the transpose to match `splev`
+        ...             out, atol=1e-15)
+        True
+
+        """
+        if isinstance(tck, BSpline):
+            t, c, k = tck.tck
+            if extrapolate is None:
+                extrapolate = tck.extrapolate
+        else:
+            t, c, k = tck
+
+        cvals = np.empty((k + 1, len(t)-1), dtype=c.dtype)
+        for m in range(k, -1, -1):
+            y = _fitpack_py.splev(t[:-1], tck, der=m)
+            cvals[k - m, :] = y/spec.gamma(m+1)
+
+        return cls.construct_fast(cvals, t, extrapolate)
+
+    @classmethod
+    def from_bernstein_basis(cls, bp, extrapolate=None):
+        """
+        Construct a piecewise polynomial in the power basis
+        from a polynomial in Bernstein basis.
+
+        Parameters
+        ----------
+        bp : BPoly
+            A Bernstein basis polynomial, as created by BPoly
+        extrapolate : bool or 'periodic', optional
+            If bool, determines whether to extrapolate to out-of-bounds points
+            based on first and last intervals, or to return NaNs.
+            If 'periodic', periodic extrapolation is used. Default is True.
+        """
+        if not isinstance(bp, BPoly):
+            raise TypeError(".from_bernstein_basis only accepts BPoly instances. "
+                            "Got %s instead." % type(bp))
+
+        dx = np.diff(bp.x)
+        k = bp.c.shape[0] - 1  # polynomial order
+
+        rest = (None,)*(bp.c.ndim-2)
+
+        c = np.zeros_like(bp.c)
+        for a in range(k+1):
+            factor = (-1)**a * comb(k, a) * bp.c[a]
+            for s in range(a, k+1):
+                val = comb(k-a, s-a) * (-1)**s
+                c[k-s] += factor * val / dx[(slice(None),)+rest]**s
+
+        if extrapolate is None:
+            extrapolate = bp.extrapolate
+
+        return cls.construct_fast(c, bp.x, extrapolate, bp.axis)
+
+
+class BPoly(_PPolyBase):
+    """Piecewise polynomial in terms of coefficients and breakpoints.
+
+    The polynomial between ``x[i]`` and ``x[i + 1]`` is written in the
+    Bernstein polynomial basis::
+
+        S = sum(c[a, i] * b(a, k; x) for a in range(k+1)),
+
+    where ``k`` is the degree of the polynomial, and::
+
+        b(a, k; x) = binom(k, a) * t**a * (1 - t)**(k - a),
+
+    with ``t = (x - x[i]) / (x[i+1] - x[i])`` and ``binom`` is the binomial
+    coefficient.
+
+    Parameters
+    ----------
+    c : ndarray, shape (k, m, ...)
+        Polynomial coefficients, order `k` and `m` intervals
+    x : ndarray, shape (m+1,)
+        Polynomial breakpoints. Must be sorted in either increasing or
+        decreasing order.
+    extrapolate : bool, optional
+        If bool, determines whether to extrapolate to out-of-bounds points
+        based on first and last intervals, or to return NaNs. If 'periodic',
+        periodic extrapolation is used. Default is True.
+    axis : int, optional
+        Interpolation axis. Default is zero.
+
+    Attributes
+    ----------
+    x : ndarray
+        Breakpoints.
+    c : ndarray
+        Coefficients of the polynomials. They are reshaped
+        to a 3-D array with the last dimension representing
+        the trailing dimensions of the original coefficient array.
+    axis : int
+        Interpolation axis.
+
+    Methods
+    -------
+    __call__
+    extend
+    derivative
+    antiderivative
+    integrate
+    construct_fast
+    from_power_basis
+    from_derivatives
+
+    See also
+    --------
+    PPoly : piecewise polynomials in the power basis
+
+    Notes
+    -----
+    Properties of Bernstein polynomials are well documented in the literature,
+    see for example [1]_ [2]_ [3]_.
+
+    References
+    ----------
+    .. [1] https://en.wikipedia.org/wiki/Bernstein_polynomial
+
+    .. [2] Kenneth I. Joy, Bernstein polynomials,
+       http://www.idav.ucdavis.edu/education/CAGDNotes/Bernstein-Polynomials.pdf
+
+    .. [3] E. H. Doha, A. H. Bhrawy, and M. A. Saker, Boundary Value Problems,
+           vol 2011, article ID 829546, :doi:`10.1155/2011/829543`.
+
+    Examples
+    --------
+    >>> from scipy.interpolate import BPoly
+    >>> x = [0, 1]
+    >>> c = [[1], [2], [3]]
+    >>> bp = BPoly(c, x)
+
+    This creates a 2nd order polynomial
+
+    .. math::
+
+        B(x) = 1 \\times b_{0, 2}(x) + 2 \\times b_{1, 2}(x) + 3
+               \\times b_{2, 2}(x) \\\\
+             = 1 \\times (1-x)^2 + 2 \\times 2 x (1 - x) + 3 \\times x^2
+
+    """  # noqa: E501
+
+    def _evaluate(self, x, nu, extrapolate, out):
+        _ppoly.evaluate_bernstein(
+            self.c.reshape(self.c.shape[0], self.c.shape[1], -1),
+            self.x, x, nu, bool(extrapolate), out)
+
+    def derivative(self, nu=1):
+        """
+        Construct a new piecewise polynomial representing the derivative.
+
+        Parameters
+        ----------
+        nu : int, optional
+            Order of derivative to evaluate. Default is 1, i.e., compute the
+            first derivative. If negative, the antiderivative is returned.
+
+        Returns
+        -------
+        bp : BPoly
+            Piecewise polynomial of order k - nu representing the derivative of
+            this polynomial.
+
+        """
+        if nu < 0:
+            return self.antiderivative(-nu)
+
+        if nu > 1:
+            bp = self
+            for k in range(nu):
+                bp = bp.derivative()
+            return bp
+
+        # reduce order
+        if nu == 0:
+            c2 = self.c.copy()
+        else:
+            # For a polynomial
+            #    B(x) = \sum_{a=0}^{k} c_a b_{a, k}(x),
+            # we use the fact that
+            #   b'_{a, k} = k ( b_{a-1, k-1} - b_{a, k-1} ),
+            # which leads to
+            #   B'(x) = \sum_{a=0}^{k-1} (c_{a+1} - c_a) b_{a, k-1}
+            #
+            # finally, for an interval [y, y + dy] with dy != 1,
+            # we need to correct for an extra power of dy
+
+            rest = (None,)*(self.c.ndim-2)
+
+            k = self.c.shape[0] - 1
+            dx = np.diff(self.x)[(None, slice(None))+rest]
+            c2 = k * np.diff(self.c, axis=0) / dx
+
+        if c2.shape[0] == 0:
+            # derivative of order 0 is zero
+            c2 = np.zeros((1,) + c2.shape[1:], dtype=c2.dtype)
+
+        # construct a compatible polynomial
+        return self.construct_fast(c2, self.x, self.extrapolate, self.axis)
+
+    def antiderivative(self, nu=1):
+        """
+        Construct a new piecewise polynomial representing the antiderivative.
+
+        Parameters
+        ----------
+        nu : int, optional
+            Order of antiderivative to evaluate. Default is 1, i.e., compute
+            the first integral. If negative, the derivative is returned.
+
+        Returns
+        -------
+        bp : BPoly
+            Piecewise polynomial of order k + nu representing the
+            antiderivative of this polynomial.
+
+        Notes
+        -----
+        If antiderivative is computed and ``self.extrapolate='periodic'``,
+        it will be set to False for the returned instance. This is done because
+        the antiderivative is no longer periodic and its correct evaluation
+        outside of the initially given x interval is difficult.
+        """
+        if nu <= 0:
+            return self.derivative(-nu)
+
+        if nu > 1:
+            bp = self
+            for k in range(nu):
+                bp = bp.antiderivative()
+            return bp
+
+        # Construct the indefinite integrals on individual intervals
+        c, x = self.c, self.x
+        k = c.shape[0]
+        c2 = np.zeros((k+1,) + c.shape[1:], dtype=c.dtype)
+
+        c2[1:, ...] = np.cumsum(c, axis=0) / k
+        delta = x[1:] - x[:-1]
+        c2 *= delta[(None, slice(None)) + (None,)*(c.ndim-2)]
+
+        # Now fix continuity: on the very first interval, take the integration
+        # constant to be zero; on an interval [x_j, x_{j+1}) with j>0,
+        # the integration constant is then equal to the jump of the `bp` at x_j.
+        # The latter is given by the coefficient of B_{n+1, n+1}
+        # *on the previous interval* (other B. polynomials are zero at the
+        # breakpoint). Finally, use the fact that BPs form a partition of unity.
+        c2[:,1:] += np.cumsum(c2[k, :], axis=0)[:-1]
+
+        if self.extrapolate == 'periodic':
+            extrapolate = False
+        else:
+            extrapolate = self.extrapolate
+
+        return self.construct_fast(c2, x, extrapolate, axis=self.axis)
+
+    def integrate(self, a, b, extrapolate=None):
+        """
+        Compute a definite integral over a piecewise polynomial.
+
+        Parameters
+        ----------
+        a : float
+            Lower integration bound
+        b : float
+            Upper integration bound
+        extrapolate : {bool, 'periodic', None}, optional
+            Whether to extrapolate to out-of-bounds points based on first
+            and last intervals, or to return NaNs. If 'periodic', periodic
+            extrapolation is used. If None (default), use `self.extrapolate`.
+
+        Returns
+        -------
+        array_like
+            Definite integral of the piecewise polynomial over [a, b]
+
+        """
+        # XXX: can probably use instead the fact that
+        # \int_0^{1} B_{j, n}(x) \dx = 1/(n+1)
+        ib = self.antiderivative()
+        if extrapolate is None:
+            extrapolate = self.extrapolate
+
+        # ib.extrapolate shouldn't be 'periodic', it is converted to
+        # False for 'periodic. in antiderivative() call.
+        if extrapolate != 'periodic':
+            ib.extrapolate = extrapolate
+
+        if extrapolate == 'periodic':
+            # Split the integral into the part over period (can be several
+            # of them) and the remaining part.
+
+            # For simplicity and clarity convert to a <= b case.
+            if a <= b:
+                sign = 1
+            else:
+                a, b = b, a
+                sign = -1
+
+            xs, xe = self.x[0], self.x[-1]
+            period = xe - xs
+            interval = b - a
+            n_periods, left = divmod(interval, period)
+            res = n_periods * (ib(xe) - ib(xs))
+
+            # Map a and b to [xs, xe].
+            a = xs + (a - xs) % period
+            b = a + left
+
+            # If b <= xe then we need to integrate over [a, b], otherwise
+            # over [a, xe] and from xs to what is remained.
+            if b <= xe:
+                res += ib(b) - ib(a)
+            else:
+                res += ib(xe) - ib(a) + ib(xs + left + a - xe) - ib(xs)
+
+            return sign * res
+        else:
+            return ib(b) - ib(a)
+
+    def extend(self, c, x):
+        k = max(self.c.shape[0], c.shape[0])
+        self.c = self._raise_degree(self.c, k - self.c.shape[0])
+        c = self._raise_degree(c, k - c.shape[0])
+        return _PPolyBase.extend(self, c, x)
+    extend.__doc__ = _PPolyBase.extend.__doc__
+
+    @classmethod
+    def from_power_basis(cls, pp, extrapolate=None):
+        """
+        Construct a piecewise polynomial in Bernstein basis
+        from a power basis polynomial.
+
+        Parameters
+        ----------
+        pp : PPoly
+            A piecewise polynomial in the power basis
+        extrapolate : bool or 'periodic', optional
+            If bool, determines whether to extrapolate to out-of-bounds points
+            based on first and last intervals, or to return NaNs.
+            If 'periodic', periodic extrapolation is used. Default is True.
+        """
+        if not isinstance(pp, PPoly):
+            raise TypeError(".from_power_basis only accepts PPoly instances. "
+                            "Got %s instead." % type(pp))
+
+        dx = np.diff(pp.x)
+        k = pp.c.shape[0] - 1   # polynomial order
+
+        rest = (None,)*(pp.c.ndim-2)
+
+        c = np.zeros_like(pp.c)
+        for a in range(k+1):
+            factor = pp.c[a] / comb(k, k-a) * dx[(slice(None),)+rest]**(k-a)
+            for j in range(k-a, k+1):
+                c[j] += factor * comb(j, k-a)
+
+        if extrapolate is None:
+            extrapolate = pp.extrapolate
+
+        return cls.construct_fast(c, pp.x, extrapolate, pp.axis)
+
+    @classmethod
+    def from_derivatives(cls, xi, yi, orders=None, extrapolate=None):
+        """Construct a piecewise polynomial in the Bernstein basis,
+        compatible with the specified values and derivatives at breakpoints.
+
+        Parameters
+        ----------
+        xi : array_like
+            sorted 1-D array of x-coordinates
+        yi : array_like or list of array_likes
+            ``yi[i][j]`` is the ``j``\\ th derivative known at ``xi[i]``
+        orders : None or int or array_like of ints. Default: None.
+            Specifies the degree of local polynomials. If not None, some
+            derivatives are ignored.
+        extrapolate : bool or 'periodic', optional
+            If bool, determines whether to extrapolate to out-of-bounds points
+            based on first and last intervals, or to return NaNs.
+            If 'periodic', periodic extrapolation is used. Default is True.
+
+        Notes
+        -----
+        If ``k`` derivatives are specified at a breakpoint ``x``, the
+        constructed polynomial is exactly ``k`` times continuously
+        differentiable at ``x``, unless the ``order`` is provided explicitly.
+        In the latter case, the smoothness of the polynomial at
+        the breakpoint is controlled by the ``order``.
+
+        Deduces the number of derivatives to match at each end
+        from ``order`` and the number of derivatives available. If
+        possible it uses the same number of derivatives from
+        each end; if the number is odd it tries to take the
+        extra one from y2. In any case if not enough derivatives
+        are available at one end or another it draws enough to
+        make up the total from the other end.
+
+        If the order is too high and not enough derivatives are available,
+        an exception is raised.
+
+        Examples
+        --------
+
+        >>> from scipy.interpolate import BPoly
+        >>> BPoly.from_derivatives([0, 1], [[1, 2], [3, 4]])
+
+        Creates a polynomial `f(x)` of degree 3, defined on `[0, 1]`
+        such that `f(0) = 1, df/dx(0) = 2, f(1) = 3, df/dx(1) = 4`
+
+        >>> BPoly.from_derivatives([0, 1, 2], [[0, 1], [0], [2]])
+
+        Creates a piecewise polynomial `f(x)`, such that
+        `f(0) = f(1) = 0`, `f(2) = 2`, and `df/dx(0) = 1`.
+        Based on the number of derivatives provided, the order of the
+        local polynomials is 2 on `[0, 1]` and 1 on `[1, 2]`.
+        Notice that no restriction is imposed on the derivatives at
+        ``x = 1`` and ``x = 2``.
+
+        Indeed, the explicit form of the polynomial is::
+
+            f(x) = | x * (1 - x),  0 <= x < 1
+                   | 2 * (x - 1),  1 <= x <= 2
+
+        So that f'(1-0) = -1 and f'(1+0) = 2
+
+        """
+        xi = np.asarray(xi)
+        if len(xi) != len(yi):
+            raise ValueError("xi and yi need to have the same length")
+        if np.any(xi[1:] - xi[:1] <= 0):
+            raise ValueError("x coordinates are not in increasing order")
+
+        # number of intervals
+        m = len(xi) - 1
+
+        # global poly order is k-1, local orders are <=k and can vary
+        try:
+            k = max(len(yi[i]) + len(yi[i+1]) for i in range(m))
+        except TypeError as e:
+            raise ValueError(
+                "Using a 1-D array for y? Please .reshape(-1, 1)."
+            ) from e
+
+        if orders is None:
+            orders = [None] * m
+        else:
+            if isinstance(orders, (int, np.integer)):
+                orders = [orders] * m
+            k = max(k, max(orders))
+
+            if any(o <= 0 for o in orders):
+                raise ValueError("Orders must be positive.")
+
+        c = []
+        for i in range(m):
+            y1, y2 = yi[i], yi[i+1]
+            if orders[i] is None:
+                n1, n2 = len(y1), len(y2)
+            else:
+                n = orders[i]+1
+                n1 = min(n//2, len(y1))
+                n2 = min(n - n1, len(y2))
+                n1 = min(n - n2, len(y2))
+                if n1+n2 != n:
+                    mesg = ("Point %g has %d derivatives, point %g"
+                            " has %d derivatives, but order %d requested" % (
+                               xi[i], len(y1), xi[i+1], len(y2), orders[i]))
+                    raise ValueError(mesg)
+
+                if not (n1 <= len(y1) and n2 <= len(y2)):
+                    raise ValueError("`order` input incompatible with"
+                                     " length y1 or y2.")
+
+            b = BPoly._construct_from_derivatives(xi[i], xi[i+1],
+                                                  y1[:n1], y2[:n2])
+            if len(b) < k:
+                b = BPoly._raise_degree(b, k - len(b))
+            c.append(b)
+
+        c = np.asarray(c)
+        return cls(c.swapaxes(0, 1), xi, extrapolate)
+
+    @staticmethod
+    def _construct_from_derivatives(xa, xb, ya, yb):
+        r"""Compute the coefficients of a polynomial in the Bernstein basis
+        given the values and derivatives at the edges.
+
+        Return the coefficients of a polynomial in the Bernstein basis
+        defined on ``[xa, xb]`` and having the values and derivatives at the
+        endpoints `xa` and `xb` as specified by `ya` and `yb`.
+        The polynomial constructed is of the minimal possible degree, i.e.,
+        if the lengths of `ya` and `yb` are `na` and `nb`, the degree
+        of the polynomial is ``na + nb - 1``.
+
+        Parameters
+        ----------
+        xa : float
+            Left-hand end point of the interval
+        xb : float
+            Right-hand end point of the interval
+        ya : array_like
+            Derivatives at `xa`. ``ya[0]`` is the value of the function, and
+            ``ya[i]`` for ``i > 0`` is the value of the ``i``\ th derivative.
+        yb : array_like
+            Derivatives at `xb`.
+
+        Returns
+        -------
+        array
+            coefficient array of a polynomial having specified derivatives
+
+        Notes
+        -----
+        This uses several facts from life of Bernstein basis functions.
+        First of all,
+
+            .. math:: b'_{a, n} = n (b_{a-1, n-1} - b_{a, n-1})
+
+        If B(x) is a linear combination of the form
+
+            .. math:: B(x) = \sum_{a=0}^{n} c_a b_{a, n},
+
+        then :math: B'(x) = n \sum_{a=0}^{n-1} (c_{a+1} - c_{a}) b_{a, n-1}.
+        Iterating the latter one, one finds for the q-th derivative
+
+            .. math:: B^{q}(x) = n!/(n-q)! \sum_{a=0}^{n-q} Q_a b_{a, n-q},
+
+        with
+
+          .. math:: Q_a = \sum_{j=0}^{q} (-)^{j+q} comb(q, j) c_{j+a}
+
+        This way, only `a=0` contributes to :math: `B^{q}(x = xa)`, and
+        `c_q` are found one by one by iterating `q = 0, ..., na`.
+
+        At ``x = xb`` it's the same with ``a = n - q``.
+
+        """
+        ya, yb = np.asarray(ya), np.asarray(yb)
+        if ya.shape[1:] != yb.shape[1:]:
+            raise ValueError('Shapes of ya {} and yb {} are incompatible'
+                             .format(ya.shape, yb.shape))
+
+        dta, dtb = ya.dtype, yb.dtype
+        if (np.issubdtype(dta, np.complexfloating) or
+               np.issubdtype(dtb, np.complexfloating)):
+            dt = np.complex128
+        else:
+            dt = np.float64
+
+        na, nb = len(ya), len(yb)
+        n = na + nb
+
+        c = np.empty((na+nb,) + ya.shape[1:], dtype=dt)
+
+        # compute coefficients of a polynomial degree na+nb-1
+        # walk left-to-right
+        for q in range(0, na):
+            c[q] = ya[q] / spec.poch(n - q, q) * (xb - xa)**q
+            for j in range(0, q):
+                c[q] -= (-1)**(j+q) * comb(q, j) * c[j]
+
+        # now walk right-to-left
+        for q in range(0, nb):
+            c[-q-1] = yb[q] / spec.poch(n - q, q) * (-1)**q * (xb - xa)**q
+            for j in range(0, q):
+                c[-q-1] -= (-1)**(j+1) * comb(q, j+1) * c[-q+j]
+
+        return c
+
+    @staticmethod
+    def _raise_degree(c, d):
+        r"""Raise a degree of a polynomial in the Bernstein basis.
+
+        Given the coefficients of a polynomial degree `k`, return (the
+        coefficients of) the equivalent polynomial of degree `k+d`.
+
+        Parameters
+        ----------
+        c : array_like
+            coefficient array, 1-D
+        d : integer
+
+        Returns
+        -------
+        array
+            coefficient array, 1-D array of length `c.shape[0] + d`
+
+        Notes
+        -----
+        This uses the fact that a Bernstein polynomial `b_{a, k}` can be
+        identically represented as a linear combination of polynomials of
+        a higher degree `k+d`:
+
+            .. math:: b_{a, k} = comb(k, a) \sum_{j=0}^{d} b_{a+j, k+d} \
+                                 comb(d, j) / comb(k+d, a+j)
+
+        """
+        if d == 0:
+            return c
+
+        k = c.shape[0] - 1
+        out = np.zeros((c.shape[0] + d,) + c.shape[1:], dtype=c.dtype)
+
+        for a in range(c.shape[0]):
+            f = c[a] * comb(k, a)
+            for j in range(d+1):
+                out[a+j] += f * comb(d, j) / comb(k+d, a+j)
+        return out
+
+
+class NdPPoly:
+    """
+    Piecewise tensor product polynomial
+
+    The value at point ``xp = (x', y', z', ...)`` is evaluated by first
+    computing the interval indices `i` such that::
+
+        x[0][i[0]] <= x' < x[0][i[0]+1]
+        x[1][i[1]] <= y' < x[1][i[1]+1]
+        ...
+
+    and then computing::
+
+        S = sum(c[k0-m0-1,...,kn-mn-1,i[0],...,i[n]]
+                * (xp[0] - x[0][i[0]])**m0
+                * ...
+                * (xp[n] - x[n][i[n]])**mn
+                for m0 in range(k[0]+1)
+                ...
+                for mn in range(k[n]+1))
+
+    where ``k[j]`` is the degree of the polynomial in dimension j. This
+    representation is the piecewise multivariate power basis.
+
+    Parameters
+    ----------
+    c : ndarray, shape (k0, ..., kn, m0, ..., mn, ...)
+        Polynomial coefficients, with polynomial order `kj` and
+        `mj+1` intervals for each dimension `j`.
+    x : ndim-tuple of ndarrays, shapes (mj+1,)
+        Polynomial breakpoints for each dimension. These must be
+        sorted in increasing order.
+    extrapolate : bool, optional
+        Whether to extrapolate to out-of-bounds points based on first
+        and last intervals, or to return NaNs. Default: True.
+
+    Attributes
+    ----------
+    x : tuple of ndarrays
+        Breakpoints.
+    c : ndarray
+        Coefficients of the polynomials.
+
+    Methods
+    -------
+    __call__
+    derivative
+    antiderivative
+    integrate
+    integrate_1d
+    construct_fast
+
+    See also
+    --------
+    PPoly : piecewise polynomials in 1D
+
+    Notes
+    -----
+    High-order polynomials in the power basis can be numerically
+    unstable.
+
+    """
+
+    def __init__(self, c, x, extrapolate=None):
+        self.x = tuple(np.ascontiguousarray(v, dtype=np.float64) for v in x)
+        self.c = np.asarray(c)
+        if extrapolate is None:
+            extrapolate = True
+        self.extrapolate = bool(extrapolate)
+
+        ndim = len(self.x)
+        if any(v.ndim != 1 for v in self.x):
+            raise ValueError("x arrays must all be 1-dimensional")
+        if any(v.size < 2 for v in self.x):
+            raise ValueError("x arrays must all contain at least 2 points")
+        if c.ndim < 2*ndim:
+            raise ValueError("c must have at least 2*len(x) dimensions")
+        if any(np.any(v[1:] - v[:-1] < 0) for v in self.x):
+            raise ValueError("x-coordinates are not in increasing order")
+        if any(a != b.size - 1 for a, b in zip(c.shape[ndim:2*ndim], self.x)):
+            raise ValueError("x and c do not agree on the number of intervals")
+
+        dtype = self._get_dtype(self.c.dtype)
+        self.c = np.ascontiguousarray(self.c, dtype=dtype)
+
+    @classmethod
+    def construct_fast(cls, c, x, extrapolate=None):
+        """
+        Construct the piecewise polynomial without making checks.
+
+        Takes the same parameters as the constructor. Input arguments
+        ``c`` and ``x`` must be arrays of the correct shape and type.  The
+        ``c`` array can only be of dtypes float and complex, and ``x``
+        array must have dtype float.
+
+        """
+        self = object.__new__(cls)
+        self.c = c
+        self.x = x
+        if extrapolate is None:
+            extrapolate = True
+        self.extrapolate = extrapolate
+        return self
+
+    def _get_dtype(self, dtype):
+        if np.issubdtype(dtype, np.complexfloating) \
+               or np.issubdtype(self.c.dtype, np.complexfloating):
+            return np.complex128
+        else:
+            return np.float64
+
+    def _ensure_c_contiguous(self):
+        if not self.c.flags.c_contiguous:
+            self.c = self.c.copy()
+        if not isinstance(self.x, tuple):
+            self.x = tuple(self.x)
+
+    def __call__(self, x, nu=None, extrapolate=None):
+        """
+        Evaluate the piecewise polynomial or its derivative
+
+        Parameters
+        ----------
+        x : array-like
+            Points to evaluate the interpolant at.
+        nu : tuple, optional
+            Orders of derivatives to evaluate. Each must be non-negative.
+        extrapolate : bool, optional
+            Whether to extrapolate to out-of-bounds points based on first
+            and last intervals, or to return NaNs.
+
+        Returns
+        -------
+        y : array-like
+            Interpolated values. Shape is determined by replacing
+            the interpolation axis in the original array with the shape of x.
+
+        Notes
+        -----
+        Derivatives are evaluated piecewise for each polynomial
+        segment, even if the polynomial is not differentiable at the
+        breakpoints. The polynomial intervals are considered half-open,
+        ``[a, b)``, except for the last interval which is closed
+        ``[a, b]``.
+
+        """
+        if extrapolate is None:
+            extrapolate = self.extrapolate
+        else:
+            extrapolate = bool(extrapolate)
+
+        ndim = len(self.x)
+
+        x = _ndim_coords_from_arrays(x)
+        x_shape = x.shape
+        x = np.ascontiguousarray(x.reshape(-1, x.shape[-1]), dtype=np.float64)
+
+        if nu is None:
+            nu = np.zeros((ndim,), dtype=np.intc)
+        else:
+            nu = np.asarray(nu, dtype=np.intc)
+            if nu.ndim != 1 or nu.shape[0] != ndim:
+                raise ValueError("invalid number of derivative orders nu")
+
+        dim1 = prod(self.c.shape[:ndim])
+        dim2 = prod(self.c.shape[ndim:2*ndim])
+        dim3 = prod(self.c.shape[2*ndim:])
+        ks = np.array(self.c.shape[:ndim], dtype=np.intc)
+
+        out = np.empty((x.shape[0], dim3), dtype=self.c.dtype)
+        self._ensure_c_contiguous()
+
+        _ppoly.evaluate_nd(self.c.reshape(dim1, dim2, dim3),
+                           self.x,
+                           ks,
+                           x,
+                           nu,
+                           bool(extrapolate),
+                           out)
+
+        return out.reshape(x_shape[:-1] + self.c.shape[2*ndim:])
+
+    def _derivative_inplace(self, nu, axis):
+        """
+        Compute 1-D derivative along a selected dimension in-place
+        May result to non-contiguous c array.
+        """
+        if nu < 0:
+            return self._antiderivative_inplace(-nu, axis)
+
+        ndim = len(self.x)
+        axis = axis % ndim
+
+        # reduce order
+        if nu == 0:
+            # noop
+            return
+        else:
+            sl = [slice(None)]*ndim
+            sl[axis] = slice(None, -nu, None)
+            c2 = self.c[tuple(sl)]
+
+        if c2.shape[axis] == 0:
+            # derivative of order 0 is zero
+            shp = list(c2.shape)
+            shp[axis] = 1
+            c2 = np.zeros(shp, dtype=c2.dtype)
+
+        # multiply by the correct rising factorials
+        factor = spec.poch(np.arange(c2.shape[axis], 0, -1), nu)
+        sl = [None]*c2.ndim
+        sl[axis] = slice(None)
+        c2 *= factor[tuple(sl)]
+
+        self.c = c2
+
+    def _antiderivative_inplace(self, nu, axis):
+        """
+        Compute 1-D antiderivative along a selected dimension
+        May result to non-contiguous c array.
+        """
+        if nu <= 0:
+            return self._derivative_inplace(-nu, axis)
+
+        ndim = len(self.x)
+        axis = axis % ndim
+
+        perm = list(range(ndim))
+        perm[0], perm[axis] = perm[axis], perm[0]
+        perm = perm + list(range(ndim, self.c.ndim))
+
+        c = self.c.transpose(perm)
+
+        c2 = np.zeros((c.shape[0] + nu,) + c.shape[1:],
+                     dtype=c.dtype)
+        c2[:-nu] = c
+
+        # divide by the correct rising factorials
+        factor = spec.poch(np.arange(c.shape[0], 0, -1), nu)
+        c2[:-nu] /= factor[(slice(None),) + (None,)*(c.ndim-1)]
+
+        # fix continuity of added degrees of freedom
+        perm2 = list(range(c2.ndim))
+        perm2[1], perm2[ndim+axis] = perm2[ndim+axis], perm2[1]
+
+        c2 = c2.transpose(perm2)
+        c2 = c2.copy()
+        _ppoly.fix_continuity(c2.reshape(c2.shape[0], c2.shape[1], -1),
+                              self.x[axis], nu-1)
+
+        c2 = c2.transpose(perm2)
+        c2 = c2.transpose(perm)
+
+        # Done
+        self.c = c2
+
+    def derivative(self, nu):
+        """
+        Construct a new piecewise polynomial representing the derivative.
+
+        Parameters
+        ----------
+        nu : ndim-tuple of int
+            Order of derivatives to evaluate for each dimension.
+            If negative, the antiderivative is returned.
+
+        Returns
+        -------
+        pp : NdPPoly
+            Piecewise polynomial of orders (k[0] - nu[0], ..., k[n] - nu[n])
+            representing the derivative of this polynomial.
+
+        Notes
+        -----
+        Derivatives are evaluated piecewise for each polynomial
+        segment, even if the polynomial is not differentiable at the
+        breakpoints. The polynomial intervals in each dimension are
+        considered half-open, ``[a, b)``, except for the last interval
+        which is closed ``[a, b]``.
+
+        """
+        p = self.construct_fast(self.c.copy(), self.x, self.extrapolate)
+
+        for axis, n in enumerate(nu):
+            p._derivative_inplace(n, axis)
+
+        p._ensure_c_contiguous()
+        return p
+
+    def antiderivative(self, nu):
+        """
+        Construct a new piecewise polynomial representing the antiderivative.
+
+        Antiderivative is also the indefinite integral of the function,
+        and derivative is its inverse operation.
+
+        Parameters
+        ----------
+        nu : ndim-tuple of int
+            Order of derivatives to evaluate for each dimension.
+            If negative, the derivative is returned.
+
+        Returns
+        -------
+        pp : PPoly
+            Piecewise polynomial of order k2 = k + n representing
+            the antiderivative of this polynomial.
+
+        Notes
+        -----
+        The antiderivative returned by this function is continuous and
+        continuously differentiable to order n-1, up to floating point
+        rounding error.
+
+        """
+        p = self.construct_fast(self.c.copy(), self.x, self.extrapolate)
+
+        for axis, n in enumerate(nu):
+            p._antiderivative_inplace(n, axis)
+
+        p._ensure_c_contiguous()
+        return p
+
+    def integrate_1d(self, a, b, axis, extrapolate=None):
+        r"""
+        Compute NdPPoly representation for one dimensional definite integral
+
+        The result is a piecewise polynomial representing the integral:
+
+        .. math::
+
+           p(y, z, ...) = \int_a^b dx\, p(x, y, z, ...)
+
+        where the dimension integrated over is specified with the
+        `axis` parameter.
+
+        Parameters
+        ----------
+        a, b : float
+            Lower and upper bound for integration.
+        axis : int
+            Dimension over which to compute the 1-D integrals
+        extrapolate : bool, optional
+            Whether to extrapolate to out-of-bounds points based on first
+            and last intervals, or to return NaNs.
+
+        Returns
+        -------
+        ig : NdPPoly or array-like
+            Definite integral of the piecewise polynomial over [a, b].
+            If the polynomial was 1D, an array is returned,
+            otherwise, an NdPPoly object.
+
+        """
+        if extrapolate is None:
+            extrapolate = self.extrapolate
+        else:
+            extrapolate = bool(extrapolate)
+
+        ndim = len(self.x)
+        axis = int(axis) % ndim
+
+        # reuse 1-D integration routines
+        c = self.c
+        swap = list(range(c.ndim))
+        swap.insert(0, swap[axis])
+        del swap[axis + 1]
+        swap.insert(1, swap[ndim + axis])
+        del swap[ndim + axis + 1]
+
+        c = c.transpose(swap)
+        p = PPoly.construct_fast(c.reshape(c.shape[0], c.shape[1], -1),
+                                 self.x[axis],
+                                 extrapolate=extrapolate)
+        out = p.integrate(a, b, extrapolate=extrapolate)
+
+        # Construct result
+        if ndim == 1:
+            return out.reshape(c.shape[2:])
+        else:
+            c = out.reshape(c.shape[2:])
+            x = self.x[:axis] + self.x[axis+1:]
+            return self.construct_fast(c, x, extrapolate=extrapolate)
+
+    def integrate(self, ranges, extrapolate=None):
+        """
+        Compute a definite integral over a piecewise polynomial.
+
+        Parameters
+        ----------
+        ranges : ndim-tuple of 2-tuples float
+            Sequence of lower and upper bounds for each dimension,
+            ``[(a[0], b[0]), ..., (a[ndim-1], b[ndim-1])]``
+        extrapolate : bool, optional
+            Whether to extrapolate to out-of-bounds points based on first
+            and last intervals, or to return NaNs.
+
+        Returns
+        -------
+        ig : array_like
+            Definite integral of the piecewise polynomial over
+            [a[0], b[0]] x ... x [a[ndim-1], b[ndim-1]]
+
+        """
+
+        ndim = len(self.x)
+
+        if extrapolate is None:
+            extrapolate = self.extrapolate
+        else:
+            extrapolate = bool(extrapolate)
+
+        if not hasattr(ranges, '__len__') or len(ranges) != ndim:
+            raise ValueError("Range not a sequence of correct length")
+
+        self._ensure_c_contiguous()
+
+        # Reuse 1D integration routine
+        c = self.c
+        for n, (a, b) in enumerate(ranges):
+            swap = list(range(c.ndim))
+            swap.insert(1, swap[ndim - n])
+            del swap[ndim - n + 1]
+
+            c = c.transpose(swap)
+
+            p = PPoly.construct_fast(c, self.x[n], extrapolate=extrapolate)
+            out = p.integrate(a, b, extrapolate=extrapolate)
+            c = out.reshape(c.shape[2:])
+
+        return c

venv/lib/python3.10/site-packages/scipy/interpolate/_ndbspline.py

@@ -0,0 +1,358 @@
+import itertools
+import functools
+import operator
+import numpy as np
+
+from math import prod
+
+from . import _bspl  # type: ignore
+
+import scipy.sparse.linalg as ssl
+from scipy.sparse import csr_array
+
+from ._bsplines import _not_a_knot
+
+__all__ = ["NdBSpline"]
+
+
+def _get_dtype(dtype):
+    """Return np.complex128 for complex dtypes, np.float64 otherwise."""
+    if np.issubdtype(dtype, np.complexfloating):
+        return np.complex128
+    else:
+        return np.float64
+
+
+class NdBSpline:
+    """Tensor product spline object.
+
+    The value at point ``xp = (x1, x2, ..., xN)`` is evaluated as a linear
+    combination of products of one-dimensional b-splines in each of the ``N``
+    dimensions::
+
+       c[i1, i2, ..., iN] * B(x1; i1, t1) * B(x2; i2, t2) * ... * B(xN; iN, tN)
+
+
+    Here ``B(x; i, t)`` is the ``i``-th b-spline defined by the knot vector
+    ``t`` evaluated at ``x``.
+
+    Parameters
+    ----------
+    t : tuple of 1D ndarrays
+        knot vectors in directions 1, 2, ... N,
+        ``len(t[i]) == n[i] + k + 1``
+    c : ndarray, shape (n1, n2, ..., nN, ...)
+        b-spline coefficients
+    k : int or length-d tuple of integers
+        spline degrees.
+        A single integer is interpreted as having this degree for
+        all dimensions.
+    extrapolate : bool, optional
+        Whether to extrapolate out-of-bounds inputs, or return `nan`.
+        Default is to extrapolate.
+
+    Attributes
+    ----------
+    t : tuple of ndarrays
+        Knots vectors.
+    c : ndarray
+        Coefficients of the tensor-produce spline.
+    k : tuple of integers
+        Degrees for each dimension.
+    extrapolate : bool, optional
+        Whether to extrapolate or return nans for out-of-bounds inputs.
+        Defaults to true.
+
+    Methods
+    -------
+    __call__
+    design_matrix
+
+    See Also
+    --------
+    BSpline : a one-dimensional B-spline object
+    NdPPoly : an N-dimensional piecewise tensor product polynomial
+
+    """
+    def __init__(self, t, c, k, *, extrapolate=None):
+        ndim = len(t)
+
+        try:
+            len(k)
+        except TypeError:
+            # make k a tuple
+            k = (k,)*ndim
+
+        if len(k) != ndim:
+            raise ValueError(f"{len(t) = } != {len(k) = }.")
+
+        self.k = tuple(operator.index(ki) for ki in k)
+        self.t = tuple(np.ascontiguousarray(ti, dtype=float) for ti in t)
+        self.c = np.asarray(c)
+
+        if extrapolate is None:
+            extrapolate = True
+        self.extrapolate = bool(extrapolate)
+
+        self.c = np.asarray(c)
+
+        for d in range(ndim):
+            td = self.t[d]
+            kd = self.k[d]
+            n = td.shape[0] - kd - 1
+            if kd < 0:
+                raise ValueError(f"Spline degree in dimension {d} cannot be"
+                                 f" negative.")
+            if td.ndim != 1:
+                raise ValueError(f"Knot vector in dimension {d} must be"
+                                 f" one-dimensional.")
+            if n < kd + 1:
+                raise ValueError(f"Need at least {2*kd + 2} knots for degree"
+                                 f" {kd} in dimension {d}.")
+            if (np.diff(td) < 0).any():
+                raise ValueError(f"Knots in dimension {d} must be in a"
+                                 f" non-decreasing order.")
+            if len(np.unique(td[kd:n + 1])) < 2:
+                raise ValueError(f"Need at least two internal knots in"
+                                 f" dimension {d}.")
+            if not np.isfinite(td).all():
+                raise ValueError(f"Knots in dimension {d} should not have"
+                                 f" nans or infs.")
+            if self.c.ndim < ndim:
+                raise ValueError(f"Coefficients must be at least"
+                                 f" {d}-dimensional.")
+            if self.c.shape[d] != n:
+                raise ValueError(f"Knots, coefficients and degree in dimension"
+                                 f" {d} are inconsistent:"
+                                 f" got {self.c.shape[d]} coefficients for"
+                                 f" {len(td)} knots, need at least {n} for"
+                                 f" k={k}.")
+
+        dt = _get_dtype(self.c.dtype)
+        self.c = np.ascontiguousarray(self.c, dtype=dt)
+
+    def __call__(self, xi, *, nu=None, extrapolate=None):
+        """Evaluate the tensor product b-spline at ``xi``.
+
+        Parameters
+        ----------
+        xi : array_like, shape(..., ndim)
+            The coordinates to evaluate the interpolator at.
+            This can be a list or tuple of ndim-dimensional points
+            or an array with the shape (num_points, ndim).
+        nu : array_like, optional, shape (ndim,)
+            Orders of derivatives to evaluate. Each must be non-negative.
+            Defaults to the zeroth derivivative.
+        extrapolate : bool, optional
+            Whether to exrapolate based on first and last intervals in each
+            dimension, or return `nan`. Default is to ``self.extrapolate``.
+
+        Returns
+        -------
+        values : ndarray, shape ``xi.shape[:-1] + self.c.shape[ndim:]``
+            Interpolated values at ``xi``
+        """
+        ndim = len(self.t)
+
+        if extrapolate is None:
+            extrapolate = self.extrapolate
+        extrapolate = bool(extrapolate)
+
+        if nu is None:
+            nu = np.zeros((ndim,), dtype=np.intc)
+        else:
+            nu = np.asarray(nu, dtype=np.intc)
+            if nu.ndim != 1 or nu.shape[0] != ndim:
+                raise ValueError(
+                    f"invalid number of derivative orders {nu = } for "
+                    f"ndim = {len(self.t)}.")
+            if any(nu < 0):
+                raise ValueError(f"derivatives must be positive, got {nu = }")
+
+        # prepare xi : shape (..., m1, ..., md) -> (1, m1, ..., md)
+        xi = np.asarray(xi, dtype=float)
+        xi_shape = xi.shape
+        xi = xi.reshape(-1, xi_shape[-1])
+        xi = np.ascontiguousarray(xi)
+
+        if xi_shape[-1] != ndim:
+            raise ValueError(f"Shapes: xi.shape={xi_shape} and ndim={ndim}")
+
+        # prepare k & t
+        _k = np.asarray(self.k, dtype=np.dtype("long"))
+
+        # pack the knots into a single array
+        len_t = [len(ti) for ti in self.t]
+        _t = np.empty((ndim, max(len_t)), dtype=float)
+        _t.fill(np.nan)
+        for d in range(ndim):
+            _t[d, :len(self.t[d])] = self.t[d]
+        len_t = np.asarray(len_t, dtype=np.dtype("long"))
+
+        # tabulate the flat indices for iterating over the (k+1)**ndim subarray
+        shape = tuple(kd + 1 for kd in self.k)
+        indices = np.unravel_index(np.arange(prod(shape)), shape)
+        _indices_k1d = np.asarray(indices, dtype=np.intp).T
+
+        # prepare the coefficients: flatten the trailing dimensions
+        c1 = self.c.reshape(self.c.shape[:ndim] + (-1,))
+        c1r = c1.ravel()
+
+        # replacement for np.ravel_multi_index for indexing of `c1`:
+        _strides_c1 = np.asarray([s // c1.dtype.itemsize
+                                  for s in c1.strides], dtype=np.intp)
+
+        num_c_tr = c1.shape[-1]  # # of trailing coefficients
+        out = np.empty(xi.shape[:-1] + (num_c_tr,), dtype=c1.dtype)
+
+        _bspl.evaluate_ndbspline(xi,
+                                 _t,
+                                 len_t,
+                                 _k,
+                                 nu,
+                                 extrapolate,
+                                 c1r,
+                                 num_c_tr,
+                                 _strides_c1,
+                                 _indices_k1d,
+                                 out,)
+
+        return out.reshape(xi_shape[:-1] + self.c.shape[ndim:])
+
+    @classmethod
+    def design_matrix(cls, xvals, t, k, extrapolate=True):
+        """Construct the design matrix as a CSR format sparse array.
+
+        Parameters
+        ----------
+        xvals :  ndarray, shape(npts, ndim)
+            Data points. ``xvals[j, :]`` gives the ``j``-th data point as an
+            ``ndim``-dimensional array.
+        t : tuple of 1D ndarrays, length-ndim
+            Knot vectors in directions 1, 2, ... ndim,
+        k : int
+            B-spline degree.
+        extrapolate : bool, optional
+            Whether to extrapolate out-of-bounds values of raise a `ValueError`
+
+        Returns
+        -------
+        design_matrix : a CSR array
+            Each row of the design matrix corresponds to a value in `xvals` and
+            contains values of b-spline basis elements which are non-zero
+            at this value.
+
+        """
+        xvals = np.asarray(xvals, dtype=float)
+        ndim = xvals.shape[-1]
+        if len(t) != ndim:
+            raise ValueError(
+                f"Data and knots are inconsistent: len(t) = {len(t)} for "
+                f" {ndim = }."
+            )
+        try:
+            len(k)
+        except TypeError:
+            # make k a tuple
+            k = (k,)*ndim
+
+        kk = np.asarray(k, dtype=np.int32)
+        data, indices, indptr = _bspl._colloc_nd(xvals, t, kk)
+        return csr_array((data, indices, indptr))
+
+
+def _iter_solve(a, b, solver=ssl.gcrotmk, **solver_args):
+    # work around iterative solvers not accepting multiple r.h.s.
+
+    # also work around a.dtype == float64 and b.dtype == complex128
+    # cf https://github.com/scipy/scipy/issues/19644
+    if np.issubdtype(b.dtype, np.complexfloating):
+        real = _iter_solve(a, b.real, solver, **solver_args)
+        imag = _iter_solve(a, b.imag, solver, **solver_args)
+        return real + 1j*imag
+
+    if b.ndim == 2 and b.shape[1] !=1:
+        res = np.empty_like(b)
+        for j in range(b.shape[1]):
+            res[:, j], info = solver(a, b[:, j], **solver_args)
+            if info != 0:
+                raise ValueError(f"{solver = } returns {info =} for column {j}.")
+        return res
+    else:
+        res, info = solver(a, b, **solver_args)
+        if info != 0:
+            raise ValueError(f"{solver = } returns {info = }.")
+        return res
+
+
+def make_ndbspl(points, values, k=3, *, solver=ssl.gcrotmk, **solver_args):
+    """Construct an interpolating NdBspline.
+
+    Parameters
+    ----------
+    points : tuple of ndarrays of float, with shapes (m1,), ... (mN,)
+        The points defining the regular grid in N dimensions. The points in
+        each dimension (i.e. every element of the `points` tuple) must be
+        strictly ascending or descending.      
+    values : ndarray of float, shape (m1, ..., mN, ...)
+        The data on the regular grid in n dimensions.
+    k : int, optional
+        The spline degree. Must be odd. Default is cubic, k=3
+    solver : a `scipy.sparse.linalg` solver (iterative or direct), optional.
+        An iterative solver from `scipy.sparse.linalg` or a direct one,
+        `sparse.sparse.linalg.spsolve`.
+        Used to solve the sparse linear system
+        ``design_matrix @ coefficients = rhs`` for the coefficients.
+        Default is `scipy.sparse.linalg.gcrotmk`
+    solver_args : dict, optional
+        Additional arguments for the solver. The call signature is
+        ``solver(csr_array, rhs_vector, **solver_args)``
+
+    Returns
+    -------
+    spl : NdBSpline object
+
+    Notes
+    -----
+    Boundary conditions are not-a-knot in all dimensions.
+    """
+    ndim = len(points)
+    xi_shape = tuple(len(x) for x in points)
+
+    try:
+        len(k)
+    except TypeError:
+        # make k a tuple
+        k = (k,)*ndim
+
+    for d, point in enumerate(points):
+        numpts = len(np.atleast_1d(point))
+        if numpts <= k[d]:
+            raise ValueError(f"There are {numpts} points in dimension {d},"
+                             f" but order {k[d]} requires at least "
+                             f" {k[d]+1} points per dimension.")
+
+    t = tuple(_not_a_knot(np.asarray(points[d], dtype=float), k[d])
+              for d in range(ndim))
+    xvals = np.asarray([xv for xv in itertools.product(*points)], dtype=float)
+
+    # construct the colocation matrix
+    matr = NdBSpline.design_matrix(xvals, t, k)
+
+    # Solve for the coefficients given `values`.
+    # Trailing dimensions: first ndim dimensions are data, the rest are batch
+    # dimensions, so stack `values` into a 2D array for `spsolve` to undestand.
+    v_shape = values.shape
+    vals_shape = (prod(v_shape[:ndim]), prod(v_shape[ndim:]))
+    vals = values.reshape(vals_shape)
+
+    if solver != ssl.spsolve:
+        solver = functools.partial(_iter_solve, solver=solver)
+        if "atol" not in solver_args:
+            # avoid a DeprecationWarning, grumble grumble
+            solver_args["atol"] = 1e-6
+
+    coef = solver(matr, vals, **solver_args)
+    coef = coef.reshape(xi_shape + v_shape[ndim:])
+    return NdBSpline(t, coef, k)
+

venv/lib/python3.10/site-packages/scipy/interpolate/_ndgriddata.py

@@ -0,0 +1,332 @@
+"""
+Convenience interface to N-D interpolation
+
+.. versionadded:: 0.9
+
+"""
+import numpy as np
+from .interpnd import LinearNDInterpolator, NDInterpolatorBase, \
+     CloughTocher2DInterpolator, _ndim_coords_from_arrays
+from scipy.spatial import cKDTree
+
+__all__ = ['griddata', 'NearestNDInterpolator', 'LinearNDInterpolator',
+           'CloughTocher2DInterpolator']
+
+#------------------------------------------------------------------------------
+# Nearest-neighbor interpolation
+#------------------------------------------------------------------------------
+
+
+class NearestNDInterpolator(NDInterpolatorBase):
+    """NearestNDInterpolator(x, y).
+
+    Nearest-neighbor interpolator in N > 1 dimensions.
+
+    .. versionadded:: 0.9
+
+    Methods
+    -------
+    __call__
+
+    Parameters
+    ----------
+    x : (npoints, ndims) 2-D ndarray of floats
+        Data point coordinates.
+    y : (npoints, ) 1-D ndarray of float or complex
+        Data values.
+    rescale : boolean, optional
+        Rescale points to unit cube before performing interpolation.
+        This is useful if some of the input dimensions have
+        incommensurable units and differ by many orders of magnitude.
+
+        .. versionadded:: 0.14.0
+    tree_options : dict, optional
+        Options passed to the underlying ``cKDTree``.
+
+        .. versionadded:: 0.17.0
+
+    See Also
+    --------
+    griddata :
+        Interpolate unstructured D-D data.
+    LinearNDInterpolator :
+        Piecewise linear interpolator in N dimensions.
+    CloughTocher2DInterpolator :
+        Piecewise cubic, C1 smooth, curvature-minimizing interpolator in 2D.
+    interpn : Interpolation on a regular grid or rectilinear grid.
+    RegularGridInterpolator : Interpolator on a regular or rectilinear grid
+                              in arbitrary dimensions (`interpn` wraps this
+                              class).
+
+    Notes
+    -----
+    Uses ``scipy.spatial.cKDTree``
+
+    .. note:: For data on a regular grid use `interpn` instead.
+
+    Examples
+    --------
+    We can interpolate values on a 2D plane:
+
+    >>> from scipy.interpolate import NearestNDInterpolator
+    >>> import numpy as np
+    >>> import matplotlib.pyplot as plt
+    >>> rng = np.random.default_rng()
+    >>> x = rng.random(10) - 0.5
+    >>> y = rng.random(10) - 0.5
+    >>> z = np.hypot(x, y)
+    >>> X = np.linspace(min(x), max(x))
+    >>> Y = np.linspace(min(y), max(y))
+    >>> X, Y = np.meshgrid(X, Y)  # 2D grid for interpolation
+    >>> interp = NearestNDInterpolator(list(zip(x, y)), z)
+    >>> Z = interp(X, Y)
+    >>> plt.pcolormesh(X, Y, Z, shading='auto')
+    >>> plt.plot(x, y, "ok", label="input point")
+    >>> plt.legend()
+    >>> plt.colorbar()
+    >>> plt.axis("equal")
+    >>> plt.show()
+
+    """
+
+    def __init__(self, x, y, rescale=False, tree_options=None):
+        NDInterpolatorBase.__init__(self, x, y, rescale=rescale,
+                                    need_contiguous=False,
+                                    need_values=False)
+        if tree_options is None:
+            tree_options = dict()
+        self.tree = cKDTree(self.points, **tree_options)
+        self.values = np.asarray(y)
+
+    def __call__(self, *args, **query_options):
+        """
+        Evaluate interpolator at given points.
+
+        Parameters
+        ----------
+        x1, x2, ... xn : array-like of float
+            Points where to interpolate data at.
+            x1, x2, ... xn can be array-like of float with broadcastable shape.
+            or x1 can be array-like of float with shape ``(..., ndim)``
+        **query_options
+            This allows ``eps``, ``p``, ``distance_upper_bound``, and ``workers``
+            being passed to the cKDTree's query function to be explicitly set.
+            See `scipy.spatial.cKDTree.query` for an overview of the different options.
+
+            .. versionadded:: 1.12.0
+
+        """
+        # For the sake of enabling subclassing, NDInterpolatorBase._set_xi performs
+        # some operations which are not required by NearestNDInterpolator.__call__, 
+        # hence here we operate on xi directly, without calling a parent class function.
+        xi = _ndim_coords_from_arrays(args, ndim=self.points.shape[1])
+        xi = self._check_call_shape(xi)
+        xi = self._scale_x(xi)
+
+        # We need to handle two important cases:
+        # (1) the case where xi has trailing dimensions (..., ndim), and
+        # (2) the case where y has trailing dimensions
+        # We will first flatten xi to deal with case (1),
+        # do the computation in flattened array while retaining y's dimensionality,
+        # and then reshape the interpolated values back to match xi's shape.
+
+        # Flatten xi for the query
+        xi_flat = xi.reshape(-1, xi.shape[-1])
+        original_shape = xi.shape
+        flattened_shape = xi_flat.shape
+
+        # if distance_upper_bound is set to not be infinite,
+        # then we need to consider the case where cKDtree
+        # does not find any points within distance_upper_bound to return.
+        # It marks those points as having infinte distance, which is what will be used
+        # below to mask the array and return only the points that were deemed
+        # to have a close enough neighbor to return something useful.
+        dist, i = self.tree.query(xi_flat, **query_options)
+        valid_mask = np.isfinite(dist)
+
+        # create a holder interp_values array and fill with nans.
+        if self.values.ndim > 1:
+            interp_shape = flattened_shape[:-1] + self.values.shape[1:]
+        else:
+            interp_shape = flattened_shape[:-1]
+
+        if np.issubdtype(self.values.dtype, np.complexfloating):
+            interp_values = np.full(interp_shape, np.nan, dtype=self.values.dtype)
+        else:
+            interp_values = np.full(interp_shape, np.nan)
+
+        interp_values[valid_mask] = self.values[i[valid_mask], ...]
+
+        if self.values.ndim > 1:
+            new_shape = original_shape[:-1] + self.values.shape[1:]
+        else:
+            new_shape = original_shape[:-1]
+        interp_values = interp_values.reshape(new_shape)
+
+        return interp_values
+
+
+#------------------------------------------------------------------------------
+# Convenience interface function
+#------------------------------------------------------------------------------
+
+
+def griddata(points, values, xi, method='linear', fill_value=np.nan,
+             rescale=False):
+    """
+    Interpolate unstructured D-D data.
+
+    Parameters
+    ----------
+    points : 2-D ndarray of floats with shape (n, D), or length D tuple of 1-D ndarrays with shape (n,).
+        Data point coordinates.
+    values : ndarray of float or complex, shape (n,)
+        Data values.
+    xi : 2-D ndarray of floats with shape (m, D), or length D tuple of ndarrays broadcastable to the same shape.
+        Points at which to interpolate data.
+    method : {'linear', 'nearest', 'cubic'}, optional
+        Method of interpolation. One of
+
+        ``nearest``
+          return the value at the data point closest to
+          the point of interpolation. See `NearestNDInterpolator` for
+          more details.
+
+        ``linear``
+          tessellate the input point set to N-D
+          simplices, and interpolate linearly on each simplex. See
+          `LinearNDInterpolator` for more details.
+
+        ``cubic`` (1-D)
+          return the value determined from a cubic
+          spline.
+
+        ``cubic`` (2-D)
+          return the value determined from a
+          piecewise cubic, continuously differentiable (C1), and
+          approximately curvature-minimizing polynomial surface. See
+          `CloughTocher2DInterpolator` for more details.
+    fill_value : float, optional
+        Value used to fill in for requested points outside of the
+        convex hull of the input points. If not provided, then the
+        default is ``nan``. This option has no effect for the
+        'nearest' method.
+    rescale : bool, optional
+        Rescale points to unit cube before performing interpolation.
+        This is useful if some of the input dimensions have
+        incommensurable units and differ by many orders of magnitude.
+
+        .. versionadded:: 0.14.0
+
+    Returns
+    -------
+    ndarray
+        Array of interpolated values.
+
+    See Also
+    --------
+    LinearNDInterpolator :
+        Piecewise linear interpolator in N dimensions.
+    NearestNDInterpolator :
+        Nearest-neighbor interpolator in N dimensions.
+    CloughTocher2DInterpolator :
+        Piecewise cubic, C1 smooth, curvature-minimizing interpolator in 2D.
+    interpn : Interpolation on a regular grid or rectilinear grid.
+    RegularGridInterpolator : Interpolator on a regular or rectilinear grid
+                              in arbitrary dimensions (`interpn` wraps this
+                              class).
+
+    Notes
+    -----
+
+    .. versionadded:: 0.9
+
+    .. note:: For data on a regular grid use `interpn` instead.
+
+    Examples
+    --------
+
+    Suppose we want to interpolate the 2-D function
+
+    >>> import numpy as np
+    >>> def func(x, y):
+    ...     return x*(1-x)*np.cos(4*np.pi*x) * np.sin(4*np.pi*y**2)**2
+
+    on a grid in [0, 1]x[0, 1]
+
+    >>> grid_x, grid_y = np.mgrid[0:1:100j, 0:1:200j]
+
+    but we only know its values at 1000 data points:
+
+    >>> rng = np.random.default_rng()
+    >>> points = rng.random((1000, 2))
+    >>> values = func(points[:,0], points[:,1])
+
+    This can be done with `griddata` -- below we try out all of the
+    interpolation methods:
+
+    >>> from scipy.interpolate import griddata
+    >>> grid_z0 = griddata(points, values, (grid_x, grid_y), method='nearest')
+    >>> grid_z1 = griddata(points, values, (grid_x, grid_y), method='linear')
+    >>> grid_z2 = griddata(points, values, (grid_x, grid_y), method='cubic')
+
+    One can see that the exact result is reproduced by all of the
+    methods to some degree, but for this smooth function the piecewise
+    cubic interpolant gives the best results:
+
+    >>> import matplotlib.pyplot as plt
+    >>> plt.subplot(221)
+    >>> plt.imshow(func(grid_x, grid_y).T, extent=(0,1,0,1), origin='lower')
+    >>> plt.plot(points[:,0], points[:,1], 'k.', ms=1)
+    >>> plt.title('Original')
+    >>> plt.subplot(222)
+    >>> plt.imshow(grid_z0.T, extent=(0,1,0,1), origin='lower')
+    >>> plt.title('Nearest')
+    >>> plt.subplot(223)
+    >>> plt.imshow(grid_z1.T, extent=(0,1,0,1), origin='lower')
+    >>> plt.title('Linear')
+    >>> plt.subplot(224)
+    >>> plt.imshow(grid_z2.T, extent=(0,1,0,1), origin='lower')
+    >>> plt.title('Cubic')
+    >>> plt.gcf().set_size_inches(6, 6)
+    >>> plt.show()
+
+    """ # numpy/numpydoc#87  # noqa: E501
+
+    points = _ndim_coords_from_arrays(points)
+
+    if points.ndim < 2:
+        ndim = points.ndim
+    else:
+        ndim = points.shape[-1]
+
+    if ndim == 1 and method in ('nearest', 'linear', 'cubic'):
+        from ._interpolate import interp1d
+        points = points.ravel()
+        if isinstance(xi, tuple):
+            if len(xi) != 1:
+                raise ValueError("invalid number of dimensions in xi")
+            xi, = xi
+        # Sort points/values together, necessary as input for interp1d
+        idx = np.argsort(points)
+        points = points[idx]
+        values = values[idx]
+        if method == 'nearest':
+            fill_value = 'extrapolate'
+        ip = interp1d(points, values, kind=method, axis=0, bounds_error=False,
+                      fill_value=fill_value)
+        return ip(xi)
+    elif method == 'nearest':
+        ip = NearestNDInterpolator(points, values, rescale=rescale)
+        return ip(xi)
+    elif method == 'linear':
+        ip = LinearNDInterpolator(points, values, fill_value=fill_value,
+                                  rescale=rescale)
+        return ip(xi)
+    elif method == 'cubic' and ndim == 2:
+        ip = CloughTocher2DInterpolator(points, values, fill_value=fill_value,
+                                        rescale=rescale)
+        return ip(xi)
+    else:
+        raise ValueError("Unknown interpolation method %r for "
+                         "%d dimensional data" % (method, ndim))

venv/lib/python3.10/site-packages/scipy/interpolate/_pade.py

@@ -0,0 +1,67 @@
+from numpy import zeros, asarray, eye, poly1d, hstack, r_
+from scipy import linalg
+
+__all__ = ["pade"]
+
+def pade(an, m, n=None):
+    """
+    Return Pade approximation to a polynomial as the ratio of two polynomials.
+
+    Parameters
+    ----------
+    an : (N,) array_like
+        Taylor series coefficients.
+    m : int
+        The order of the returned approximating polynomial `q`.
+    n : int, optional
+        The order of the returned approximating polynomial `p`. By default,
+        the order is ``len(an)-1-m``.
+
+    Returns
+    -------
+    p, q : Polynomial class
+        The Pade approximation of the polynomial defined by `an` is
+        ``p(x)/q(x)``.
+
+    Examples
+    --------
+    >>> import numpy as np
+    >>> from scipy.interpolate import pade
+    >>> e_exp = [1.0, 1.0, 1.0/2.0, 1.0/6.0, 1.0/24.0, 1.0/120.0]
+    >>> p, q = pade(e_exp, 2)
+
+    >>> e_exp.reverse()
+    >>> e_poly = np.poly1d(e_exp)
+
+    Compare ``e_poly(x)`` and the Pade approximation ``p(x)/q(x)``
+
+    >>> e_poly(1)
+    2.7166666666666668
+
+    >>> p(1)/q(1)
+    2.7179487179487181
+
+    """
+    an = asarray(an)
+    if n is None:
+        n = len(an) - 1 - m
+        if n < 0:
+            raise ValueError("Order of q <m> must be smaller than len(an)-1.")
+    if n < 0:
+        raise ValueError("Order of p <n> must be greater than 0.")
+    N = m + n
+    if N > len(an)-1:
+        raise ValueError("Order of q+p <m+n> must be smaller than len(an).")
+    an = an[:N+1]
+    Akj = eye(N+1, n+1, dtype=an.dtype)
+    Bkj = zeros((N+1, m), dtype=an.dtype)
+    for row in range(1, m+1):
+        Bkj[row,:row] = -(an[:row])[::-1]
+    for row in range(m+1, N+1):
+        Bkj[row,:] = -(an[row-m:row])[::-1]
+    C = hstack((Akj, Bkj))
+    pq = linalg.solve(C, an)
+    p = pq[:n+1]
+    q = r_[1.0, pq[n+1:]]
+    return poly1d(p[::-1]), poly1d(q[::-1])
+

venv/lib/python3.10/site-packages/scipy/interpolate/_polyint.py

@@ -0,0 +1,938 @@
+import warnings
+
+import numpy as np
+from scipy.special import factorial
+from scipy._lib._util import _asarray_validated, float_factorial, check_random_state
+
+
+__all__ = ["KroghInterpolator", "krogh_interpolate",
+           "BarycentricInterpolator", "barycentric_interpolate",
+           "approximate_taylor_polynomial"]
+
+
+def _isscalar(x):
+    """Check whether x is if a scalar type, or 0-dim"""
+    return np.isscalar(x) or hasattr(x, 'shape') and x.shape == ()
+
+
+class _Interpolator1D:
+    """
+    Common features in univariate interpolation
+
+    Deal with input data type and interpolation axis rolling. The
+    actual interpolator can assume the y-data is of shape (n, r) where
+    `n` is the number of x-points, and `r` the number of variables,
+    and use self.dtype as the y-data type.
+
+    Attributes
+    ----------
+    _y_axis
+        Axis along which the interpolation goes in the original array
+    _y_extra_shape
+        Additional trailing shape of the input arrays, excluding
+        the interpolation axis.
+    dtype
+        Dtype of the y-data arrays. Can be set via _set_dtype, which
+        forces it to be float or complex.
+
+    Methods
+    -------
+    __call__
+    _prepare_x
+    _finish_y
+    _reshape_yi
+    _set_yi
+    _set_dtype
+    _evaluate
+
+    """
+
+    __slots__ = ('_y_axis', '_y_extra_shape', 'dtype')
+
+    def __init__(self, xi=None, yi=None, axis=None):
+        self._y_axis = axis
+        self._y_extra_shape = None
+        self.dtype = None
+        if yi is not None:
+            self._set_yi(yi, xi=xi, axis=axis)
+
+    def __call__(self, x):
+        """
+        Evaluate the interpolant
+
+        Parameters
+        ----------
+        x : array_like
+            Point or points at which to evaluate the interpolant.
+
+        Returns
+        -------
+        y : array_like
+            Interpolated values. Shape is determined by replacing
+            the interpolation axis in the original array with the shape of `x`.
+
+        Notes
+        -----
+        Input values `x` must be convertible to `float` values like `int`
+        or `float`.
+
+        """
+        x, x_shape = self._prepare_x(x)
+        y = self._evaluate(x)
+        return self._finish_y(y, x_shape)
+
+    def _evaluate(self, x):
+        """
+        Actually evaluate the value of the interpolator.
+        """
+        raise NotImplementedError()
+
+    def _prepare_x(self, x):
+        """Reshape input x array to 1-D"""
+        x = _asarray_validated(x, check_finite=False, as_inexact=True)
+        x_shape = x.shape
+        return x.ravel(), x_shape
+
+    def _finish_y(self, y, x_shape):
+        """Reshape interpolated y back to an N-D array similar to initial y"""
+        y = y.reshape(x_shape + self._y_extra_shape)
+        if self._y_axis != 0 and x_shape != ():
+            nx = len(x_shape)
+            ny = len(self._y_extra_shape)
+            s = (list(range(nx, nx + self._y_axis))
+                 + list(range(nx)) + list(range(nx+self._y_axis, nx+ny)))
+            y = y.transpose(s)
+        return y
+
+    def _reshape_yi(self, yi, check=False):
+        yi = np.moveaxis(np.asarray(yi), self._y_axis, 0)
+        if check and yi.shape[1:] != self._y_extra_shape:
+            ok_shape = "{!r} + (N,) + {!r}".format(self._y_extra_shape[-self._y_axis:],
+                                                   self._y_extra_shape[:-self._y_axis])
+            raise ValueError("Data must be of shape %s" % ok_shape)
+        return yi.reshape((yi.shape[0], -1))
+
+    def _set_yi(self, yi, xi=None, axis=None):
+        if axis is None:
+            axis = self._y_axis
+        if axis is None:
+            raise ValueError("no interpolation axis specified")
+
+        yi = np.asarray(yi)
+
+        shape = yi.shape
+        if shape == ():
+            shape = (1,)
+        if xi is not None and shape[axis] != len(xi):
+            raise ValueError("x and y arrays must be equal in length along "
+                             "interpolation axis.")
+
+        self._y_axis = (axis % yi.ndim)
+        self._y_extra_shape = yi.shape[:self._y_axis] + yi.shape[self._y_axis+1:]
+        self.dtype = None
+        self._set_dtype(yi.dtype)
+
+    def _set_dtype(self, dtype, union=False):
+        if np.issubdtype(dtype, np.complexfloating) \
+               or np.issubdtype(self.dtype, np.complexfloating):
+            self.dtype = np.complex128
+        else:
+            if not union or self.dtype != np.complex128:
+                self.dtype = np.float64
+
+
+class _Interpolator1DWithDerivatives(_Interpolator1D):
+    def derivatives(self, x, der=None):
+        """
+        Evaluate several derivatives of the polynomial at the point `x`
+
+        Produce an array of derivatives evaluated at the point `x`.
+
+        Parameters
+        ----------
+        x : array_like
+            Point or points at which to evaluate the derivatives
+        der : int or list or None, optional
+            How many derivatives to evaluate, or None for all potentially
+            nonzero derivatives (that is, a number equal to the number
+            of points), or a list of derivatives to evaluate. This number
+            includes the function value as the '0th' derivative.
+
+        Returns
+        -------
+        d : ndarray
+            Array with derivatives; ``d[j]`` contains the jth derivative.
+            Shape of ``d[j]`` is determined by replacing the interpolation
+            axis in the original array with the shape of `x`.
+
+        Examples
+        --------
+        >>> from scipy.interpolate import KroghInterpolator
+        >>> KroghInterpolator([0,0,0],[1,2,3]).derivatives(0)
+        array([1.0,2.0,3.0])
+        >>> KroghInterpolator([0,0,0],[1,2,3]).derivatives([0,0])
+        array([[1.0,1.0],
+               [2.0,2.0],
+               [3.0,3.0]])
+
+        """
+        x, x_shape = self._prepare_x(x)
+        y = self._evaluate_derivatives(x, der)
+
+        y = y.reshape((y.shape[0],) + x_shape + self._y_extra_shape)
+        if self._y_axis != 0 and x_shape != ():
+            nx = len(x_shape)
+            ny = len(self._y_extra_shape)
+            s = ([0] + list(range(nx+1, nx + self._y_axis+1))
+                 + list(range(1, nx+1)) +
+                 list(range(nx+1+self._y_axis, nx+ny+1)))
+            y = y.transpose(s)
+        return y
+
+    def derivative(self, x, der=1):
+        """
+        Evaluate a single derivative of the polynomial at the point `x`.
+
+        Parameters
+        ----------
+        x : array_like
+            Point or points at which to evaluate the derivatives
+
+        der : integer, optional
+            Which derivative to evaluate (default: first derivative).
+            This number includes the function value as 0th derivative.
+
+        Returns
+        -------
+        d : ndarray
+            Derivative interpolated at the x-points. Shape of `d` is
+            determined by replacing the interpolation axis in the
+            original array with the shape of `x`.
+
+        Notes
+        -----
+        This may be computed by evaluating all derivatives up to the desired
+        one (using self.derivatives()) and then discarding the rest.
+
+        """
+        x, x_shape = self._prepare_x(x)
+        y = self._evaluate_derivatives(x, der+1)
+        return self._finish_y(y[der], x_shape)
+
+    def _evaluate_derivatives(self, x, der=None):
+        """
+        Actually evaluate the derivatives.
+
+        Parameters
+        ----------
+        x : array_like
+            1D array of points at which to evaluate the derivatives
+        der : integer, optional
+            The number of derivatives to evaluate, from 'order 0' (der=1)
+            to order der-1.  If omitted, return all possibly-non-zero
+            derivatives, ie 0 to order n-1.
+
+        Returns
+        -------
+        d : ndarray
+            Array of shape ``(der, x.size, self.yi.shape[1])`` containing
+            the derivatives from 0 to der-1
+        """
+        raise NotImplementedError()
+
+
+class KroghInterpolator(_Interpolator1DWithDerivatives):
+    """
+    Interpolating polynomial for a set of points.
+
+    The polynomial passes through all the pairs ``(xi, yi)``. One may
+    additionally specify a number of derivatives at each point `xi`;
+    this is done by repeating the value `xi` and specifying the
+    derivatives as successive `yi` values.
+
+    Allows evaluation of the polynomial and all its derivatives.
+    For reasons of numerical stability, this function does not compute
+    the coefficients of the polynomial, although they can be obtained
+    by evaluating all the derivatives.
+
+    Parameters
+    ----------
+    xi : array_like, shape (npoints, )
+        Known x-coordinates. Must be sorted in increasing order.
+    yi : array_like, shape (..., npoints, ...)
+        Known y-coordinates. When an xi occurs two or more times in
+        a row, the corresponding yi's represent derivative values. The length of `yi`
+        along the interpolation axis must be equal to the length of `xi`. Use the
+        `axis` parameter to select the correct axis.
+    axis : int, optional
+        Axis in the `yi` array corresponding to the x-coordinate values. Defaults to
+        ``axis=0``.
+
+    Notes
+    -----
+    Be aware that the algorithms implemented here are not necessarily
+    the most numerically stable known. Moreover, even in a world of
+    exact computation, unless the x coordinates are chosen very
+    carefully - Chebyshev zeros (e.g., cos(i*pi/n)) are a good choice -
+    polynomial interpolation itself is a very ill-conditioned process
+    due to the Runge phenomenon. In general, even with well-chosen
+    x values, degrees higher than about thirty cause problems with
+    numerical instability in this code.
+
+    Based on [1]_.
+
+    References
+    ----------
+    .. [1] Krogh, "Efficient Algorithms for Polynomial Interpolation
+        and Numerical Differentiation", 1970.
+
+    Examples
+    --------
+    To produce a polynomial that is zero at 0 and 1 and has
+    derivative 2 at 0, call
+
+    >>> from scipy.interpolate import KroghInterpolator
+    >>> KroghInterpolator([0,0,1],[0,2,0])
+
+    This constructs the quadratic :math:`2x^2-2x`. The derivative condition
+    is indicated by the repeated zero in the `xi` array; the corresponding
+    yi values are 0, the function value, and 2, the derivative value.
+
+    For another example, given `xi`, `yi`, and a derivative `ypi` for each
+    point, appropriate arrays can be constructed as:
+
+    >>> import numpy as np
+    >>> rng = np.random.default_rng()
+    >>> xi = np.linspace(0, 1, 5)
+    >>> yi, ypi = rng.random((2, 5))
+    >>> xi_k, yi_k = np.repeat(xi, 2), np.ravel(np.dstack((yi,ypi)))
+    >>> KroghInterpolator(xi_k, yi_k)
+
+    To produce a vector-valued polynomial, supply a higher-dimensional
+    array for `yi`:
+
+    >>> KroghInterpolator([0,1],[[2,3],[4,5]])
+
+    This constructs a linear polynomial giving (2,3) at 0 and (4,5) at 1.
+
+    """
+
+    def __init__(self, xi, yi, axis=0):
+        super().__init__(xi, yi, axis)
+
+        self.xi = np.asarray(xi)
+        self.yi = self._reshape_yi(yi)
+        self.n, self.r = self.yi.shape
+
+        if (deg := self.xi.size) > 30:
+            warnings.warn(f"{deg} degrees provided, degrees higher than about"
+                          " thirty cause problems with numerical instability "
+                          "with 'KroghInterpolator'", stacklevel=2)
+
+        c = np.zeros((self.n+1, self.r), dtype=self.dtype)
+        c[0] = self.yi[0]
+        Vk = np.zeros((self.n, self.r), dtype=self.dtype)
+        for k in range(1, self.n):
+            s = 0
+            while s <= k and xi[k-s] == xi[k]:
+                s += 1
+            s -= 1
+            Vk[0] = self.yi[k]/float_factorial(s)
+            for i in range(k-s):
+                if xi[i] == xi[k]:
+                    raise ValueError("Elements of `xi` can't be equal.")
+                if s == 0:
+                    Vk[i+1] = (c[i]-Vk[i])/(xi[i]-xi[k])
+                else:
+                    Vk[i+1] = (Vk[i+1]-Vk[i])/(xi[i]-xi[k])
+            c[k] = Vk[k-s]
+        self.c = c
+
+    def _evaluate(self, x):
+        pi = 1
+        p = np.zeros((len(x), self.r), dtype=self.dtype)
+        p += self.c[0,np.newaxis,:]
+        for k in range(1, self.n):
+            w = x - self.xi[k-1]
+            pi = w*pi
+            p += pi[:,np.newaxis] * self.c[k]
+        return p
+
+    def _evaluate_derivatives(self, x, der=None):
+        n = self.n
+        r = self.r
+
+        if der is None:
+            der = self.n
+
+        pi = np.zeros((n, len(x)))
+        w = np.zeros((n, len(x)))
+        pi[0] = 1
+        p = np.zeros((len(x), self.r), dtype=self.dtype)
+        p += self.c[0, np.newaxis, :]
+
+        for k in range(1, n):
+            w[k-1] = x - self.xi[k-1]
+            pi[k] = w[k-1] * pi[k-1]
+            p += pi[k, :, np.newaxis] * self.c[k]
+
+        cn = np.zeros((max(der, n+1), len(x), r), dtype=self.dtype)
+        cn[:n+1, :, :] += self.c[:n+1, np.newaxis, :]
+        cn[0] = p
+        for k in range(1, n):
+            for i in range(1, n-k+1):
+                pi[i] = w[k+i-1]*pi[i-1] + pi[i]
+                cn[k] = cn[k] + pi[i, :, np.newaxis]*cn[k+i]
+            cn[k] *= float_factorial(k)
+
+        cn[n, :, :] = 0
+        return cn[:der]
+
+
+def krogh_interpolate(xi, yi, x, der=0, axis=0):
+    """
+    Convenience function for polynomial interpolation.
+
+    See `KroghInterpolator` for more details.
+
+    Parameters
+    ----------
+    xi : array_like
+        Interpolation points (known x-coordinates).
+    yi : array_like
+        Known y-coordinates, of shape ``(xi.size, R)``. Interpreted as
+        vectors of length R, or scalars if R=1.
+    x : array_like
+        Point or points at which to evaluate the derivatives.
+    der : int or list or None, optional
+        How many derivatives to evaluate, or None for all potentially
+        nonzero derivatives (that is, a number equal to the number
+        of points), or a list of derivatives to evaluate. This number
+        includes the function value as the '0th' derivative.
+    axis : int, optional
+        Axis in the `yi` array corresponding to the x-coordinate values.
+
+    Returns
+    -------
+    d : ndarray
+        If the interpolator's values are R-D then the
+        returned array will be the number of derivatives by N by R.
+        If `x` is a scalar, the middle dimension will be dropped; if
+        the `yi` are scalars then the last dimension will be dropped.
+
+    See Also
+    --------
+    KroghInterpolator : Krogh interpolator
+
+    Notes
+    -----
+    Construction of the interpolating polynomial is a relatively expensive
+    process. If you want to evaluate it repeatedly consider using the class
+    KroghInterpolator (which is what this function uses).
+
+    Examples
+    --------
+    We can interpolate 2D observed data using Krogh interpolation:
+
+    >>> import numpy as np
+    >>> import matplotlib.pyplot as plt
+    >>> from scipy.interpolate import krogh_interpolate
+    >>> x_observed = np.linspace(0.0, 10.0, 11)
+    >>> y_observed = np.sin(x_observed)
+    >>> x = np.linspace(min(x_observed), max(x_observed), num=100)
+    >>> y = krogh_interpolate(x_observed, y_observed, x)
+    >>> plt.plot(x_observed, y_observed, "o", label="observation")
+    >>> plt.plot(x, y, label="krogh interpolation")
+    >>> plt.legend()
+    >>> plt.show()
+    """
+
+    P = KroghInterpolator(xi, yi, axis=axis)
+    if der == 0:
+        return P(x)
+    elif _isscalar(der):
+        return P.derivative(x, der=der)
+    else:
+        return P.derivatives(x, der=np.amax(der)+1)[der]
+
+
+def approximate_taylor_polynomial(f,x,degree,scale,order=None):
+    """
+    Estimate the Taylor polynomial of f at x by polynomial fitting.
+
+    Parameters
+    ----------
+    f : callable
+        The function whose Taylor polynomial is sought. Should accept
+        a vector of `x` values.
+    x : scalar
+        The point at which the polynomial is to be evaluated.
+    degree : int
+        The degree of the Taylor polynomial
+    scale : scalar
+        The width of the interval to use to evaluate the Taylor polynomial.
+        Function values spread over a range this wide are used to fit the
+        polynomial. Must be chosen carefully.
+    order : int or None, optional
+        The order of the polynomial to be used in the fitting; `f` will be
+        evaluated ``order+1`` times. If None, use `degree`.
+
+    Returns
+    -------
+    p : poly1d instance
+        The Taylor polynomial (translated to the origin, so that
+        for example p(0)=f(x)).
+
+    Notes
+    -----
+    The appropriate choice of "scale" is a trade-off; too large and the
+    function differs from its Taylor polynomial too much to get a good
+    answer, too small and round-off errors overwhelm the higher-order terms.
+    The algorithm used becomes numerically unstable around order 30 even
+    under ideal circumstances.
+
+    Choosing order somewhat larger than degree may improve the higher-order
+    terms.
+
+    Examples
+    --------
+    We can calculate Taylor approximation polynomials of sin function with
+    various degrees:
+
+    >>> import numpy as np
+    >>> import matplotlib.pyplot as plt
+    >>> from scipy.interpolate import approximate_taylor_polynomial
+    >>> x = np.linspace(-10.0, 10.0, num=100)
+    >>> plt.plot(x, np.sin(x), label="sin curve")
+    >>> for degree in np.arange(1, 15, step=2):
+    ...     sin_taylor = approximate_taylor_polynomial(np.sin, 0, degree, 1,
+    ...                                                order=degree + 2)
+    ...     plt.plot(x, sin_taylor(x), label=f"degree={degree}")
+    >>> plt.legend(bbox_to_anchor=(1.05, 1), loc='upper left',
+    ...            borderaxespad=0.0, shadow=True)
+    >>> plt.tight_layout()
+    >>> plt.axis([-10, 10, -10, 10])
+    >>> plt.show()
+
+    """
+    if order is None:
+        order = degree
+
+    n = order+1
+    # Choose n points that cluster near the endpoints of the interval in
+    # a way that avoids the Runge phenomenon. Ensure, by including the
+    # endpoint or not as appropriate, that one point always falls at x
+    # exactly.
+    xs = scale*np.cos(np.linspace(0,np.pi,n,endpoint=n % 1)) + x
+
+    P = KroghInterpolator(xs, f(xs))
+    d = P.derivatives(x,der=degree+1)
+
+    return np.poly1d((d/factorial(np.arange(degree+1)))[::-1])
+
+
+class BarycentricInterpolator(_Interpolator1DWithDerivatives):
+    r"""Interpolating polynomial for a set of points.
+
+    Constructs a polynomial that passes through a given set of points.
+    Allows evaluation of the polynomial and all its derivatives,
+    efficient changing of the y-values to be interpolated,
+    and updating by adding more x- and y-values.
+
+    For reasons of numerical stability, this function does not compute
+    the coefficients of the polynomial.
+
+    The values `yi` need to be provided before the function is
+    evaluated, but none of the preprocessing depends on them, so rapid
+    updates are possible.
+
+    Parameters
+    ----------
+    xi : array_like, shape (npoints, )
+        1-D array of x coordinates of the points the polynomial
+        should pass through
+    yi : array_like, shape (..., npoints, ...), optional
+        N-D array of y coordinates of the points the polynomial should pass through.
+        If None, the y values will be supplied later via the `set_y` method.
+        The length of `yi` along the interpolation axis must be equal to the length
+        of `xi`. Use the ``axis`` parameter to select correct axis.
+    axis : int, optional
+        Axis in the yi array corresponding to the x-coordinate values. Defaults
+        to ``axis=0``.
+    wi : array_like, optional
+        The barycentric weights for the chosen interpolation points `xi`.
+        If absent or None, the weights will be computed from `xi` (default).
+        This allows for the reuse of the weights `wi` if several interpolants
+        are being calculated using the same nodes `xi`, without re-computation.
+    random_state : {None, int, `numpy.random.Generator`, `numpy.random.RandomState`}, optional
+        If `seed` is None (or `np.random`), the `numpy.random.RandomState`
+        singleton is used.
+        If `seed` is an int, a new ``RandomState`` instance is used,
+        seeded with `seed`.
+        If `seed` is already a ``Generator`` or ``RandomState`` instance then
+        that instance is used.
+
+    Notes
+    -----
+    This class uses a "barycentric interpolation" method that treats
+    the problem as a special case of rational function interpolation.
+    This algorithm is quite stable, numerically, but even in a world of
+    exact computation, unless the x coordinates are chosen very
+    carefully - Chebyshev zeros (e.g., cos(i*pi/n)) are a good choice -
+    polynomial interpolation itself is a very ill-conditioned process
+    due to the Runge phenomenon.
+
+    Based on Berrut and Trefethen 2004, "Barycentric Lagrange Interpolation".
+
+    Examples
+    --------
+    To produce a quintic barycentric interpolant approximating the function
+    :math:`\sin x`, and its first four derivatives, using six randomly-spaced
+    nodes in :math:`(0, \frac{\pi}{2})`:
+
+    >>> import numpy as np
+    >>> import matplotlib.pyplot as plt
+    >>> from scipy.interpolate import BarycentricInterpolator
+    >>> rng = np.random.default_rng()
+    >>> xi = rng.random(6) * np.pi/2
+    >>> f, f_d1, f_d2, f_d3, f_d4 = np.sin, np.cos, lambda x: -np.sin(x), lambda x: -np.cos(x), np.sin
+    >>> P = BarycentricInterpolator(xi, f(xi), random_state=rng)
+    >>> fig, axs = plt.subplots(5, 1, sharex=True, layout='constrained', figsize=(7,10))
+    >>> x = np.linspace(0, np.pi, 100)
+    >>> axs[0].plot(x, P(x), 'r:', x, f(x), 'k--', xi, f(xi), 'xk')
+    >>> axs[1].plot(x, P.derivative(x), 'r:', x, f_d1(x), 'k--', xi, f_d1(xi), 'xk')
+    >>> axs[2].plot(x, P.derivative(x, 2), 'r:', x, f_d2(x), 'k--', xi, f_d2(xi), 'xk')
+    >>> axs[3].plot(x, P.derivative(x, 3), 'r:', x, f_d3(x), 'k--', xi, f_d3(xi), 'xk')
+    >>> axs[4].plot(x, P.derivative(x, 4), 'r:', x, f_d4(x), 'k--', xi, f_d4(xi), 'xk')
+    >>> axs[0].set_xlim(0, np.pi)
+    >>> axs[4].set_xlabel(r"$x$")
+    >>> axs[4].set_xticks([i * np.pi / 4 for i in range(5)],
+    ...                   ["0", r"$\frac{\pi}{4}$", r"$\frac{\pi}{2}$", r"$\frac{3\pi}{4}$", r"$\pi$"])
+    >>> axs[0].set_ylabel("$f(x)$")
+    >>> axs[1].set_ylabel("$f'(x)$")
+    >>> axs[2].set_ylabel("$f''(x)$")
+    >>> axs[3].set_ylabel("$f^{(3)}(x)$")
+    >>> axs[4].set_ylabel("$f^{(4)}(x)$")
+    >>> labels = ['Interpolation nodes', 'True function $f$', 'Barycentric interpolation']
+    >>> axs[0].legend(axs[0].get_lines()[::-1], labels, bbox_to_anchor=(0., 1.02, 1., .102),
+    ...               loc='lower left', ncols=3, mode="expand", borderaxespad=0., frameon=False)
+    >>> plt.show()
+    """ # numpy/numpydoc#87  # noqa: E501
+
+    def __init__(self, xi, yi=None, axis=0, *, wi=None, random_state=None):
+        super().__init__(xi, yi, axis)
+        
+        random_state = check_random_state(random_state)
+
+        self.xi = np.asarray(xi, dtype=np.float64)
+        self.set_yi(yi)
+        self.n = len(self.xi)
+
+        # cache derivative object to avoid re-computing the weights with every call.
+        self._diff_cij = None
+
+        if wi is not None:
+            self.wi = wi
+        else:
+            # See page 510 of Berrut and Trefethen 2004 for an explanation of the
+            # capacity scaling and the suggestion of using a random permutation of
+            # the input factors.
+            # At the moment, the permutation is not performed for xi that are
+            # appended later through the add_xi interface. It's not clear to me how
+            # to implement that and it seems that most situations that require
+            # these numerical stability improvements will be able to provide all
+            # the points to the constructor.
+            self._inv_capacity = 4.0 / (np.max(self.xi) - np.min(self.xi))
+            permute = random_state.permutation(self.n, )
+            inv_permute = np.zeros(self.n, dtype=np.int32)
+            inv_permute[permute] = np.arange(self.n)
+            self.wi = np.zeros(self.n)
+
+            for i in range(self.n):
+                dist = self._inv_capacity * (self.xi[i] - self.xi[permute])
+                dist[inv_permute[i]] = 1.0
+                prod = np.prod(dist)
+                if prod == 0.0:
+                    raise ValueError("Interpolation points xi must be"
+                                     " distinct.")
+                self.wi[i] = 1.0 / prod
+
+    def set_yi(self, yi, axis=None):
+        """
+        Update the y values to be interpolated
+
+        The barycentric interpolation algorithm requires the calculation
+        of weights, but these depend only on the `xi`. The `yi` can be changed
+        at any time.
+
+        Parameters
+        ----------
+        yi : array_like
+            The y-coordinates of the points the polynomial will pass through.
+            If None, the y values must be supplied later.
+        axis : int, optional
+            Axis in the `yi` array corresponding to the x-coordinate values.
+
+        """
+        if yi is None:
+            self.yi = None
+            return
+        self._set_yi(yi, xi=self.xi, axis=axis)
+        self.yi = self._reshape_yi(yi)
+        self.n, self.r = self.yi.shape
+        self._diff_baryint = None
+
+    def add_xi(self, xi, yi=None):
+        """
+        Add more x values to the set to be interpolated
+
+        The barycentric interpolation algorithm allows easy updating by
+        adding more points for the polynomial to pass through.
+
+        Parameters
+        ----------
+        xi : array_like
+            The x coordinates of the points that the polynomial should pass
+            through.
+        yi : array_like, optional
+            The y coordinates of the points the polynomial should pass through.
+            Should have shape ``(xi.size, R)``; if R > 1 then the polynomial is
+            vector-valued.
+            If `yi` is not given, the y values will be supplied later. `yi`
+            should be given if and only if the interpolator has y values
+            specified.
+
+        Notes
+        -----
+        The new points added by `add_xi` are not randomly permuted
+        so there is potential for numerical instability,
+        especially for a large number of points. If this
+        happens, please reconstruct interpolation from scratch instead.
+        """
+        if yi is not None:
+            if self.yi is None:
+                raise ValueError("No previous yi value to update!")
+            yi = self._reshape_yi(yi, check=True)
+            self.yi = np.vstack((self.yi,yi))
+        else:
+            if self.yi is not None:
+                raise ValueError("No update to yi provided!")
+        old_n = self.n
+        self.xi = np.concatenate((self.xi,xi))
+        self.n = len(self.xi)
+        self.wi **= -1
+        old_wi = self.wi
+        self.wi = np.zeros(self.n)
+        self.wi[:old_n] = old_wi
+        for j in range(old_n, self.n):
+            self.wi[:j] *= self._inv_capacity * (self.xi[j]-self.xi[:j])
+            self.wi[j] = np.multiply.reduce(
+                self._inv_capacity * (self.xi[:j]-self.xi[j])
+            )
+        self.wi **= -1
+        self._diff_cij = None
+        self._diff_baryint = None
+
+    def __call__(self, x):
+        """Evaluate the interpolating polynomial at the points x
+
+        Parameters
+        ----------
+        x : array_like
+            Point or points at which to evaluate the interpolant.
+
+        Returns
+        -------
+        y : array_like
+            Interpolated values. Shape is determined by replacing
+            the interpolation axis in the original array with the shape of `x`.
+
+        Notes
+        -----
+        Currently the code computes an outer product between `x` and the
+        weights, that is, it constructs an intermediate array of size
+        ``(N, len(x))``, where N is the degree of the polynomial.
+        """
+        return _Interpolator1D.__call__(self, x)
+
+    def _evaluate(self, x):
+        if x.size == 0:
+            p = np.zeros((0, self.r), dtype=self.dtype)
+        else:
+            c = x[..., np.newaxis] - self.xi
+            z = c == 0
+            c[z] = 1
+            c = self.wi / c
+            with np.errstate(divide='ignore'):
+                p = np.dot(c, self.yi) / np.sum(c, axis=-1)[..., np.newaxis]
+            # Now fix where x==some xi
+            r = np.nonzero(z)
+            if len(r) == 1:  # evaluation at a scalar
+                if len(r[0]) > 0:  # equals one of the points
+                    p = self.yi[r[0][0]]
+            else:
+                p[r[:-1]] = self.yi[r[-1]]
+        return p
+
+    def derivative(self, x, der=1):
+        """
+        Evaluate a single derivative of the polynomial at the point x.
+
+        Parameters
+        ----------
+        x : array_like
+            Point or points at which to evaluate the derivatives
+        der : integer, optional
+            Which derivative to evaluate (default: first derivative).
+            This number includes the function value as 0th derivative.
+
+        Returns
+        -------
+        d : ndarray
+            Derivative interpolated at the x-points. Shape of `d` is
+            determined by replacing the interpolation axis in the
+            original array with the shape of `x`.
+        """
+        x, x_shape = self._prepare_x(x)
+        y = self._evaluate_derivatives(x, der+1, all_lower=False)
+        return self._finish_y(y, x_shape)
+
+    def _evaluate_derivatives(self, x, der=None, all_lower=True):
+        # NB: der here is not the order of the highest derivative;
+        # instead, it is the size of the derivatives matrix that
+        # would be returned with all_lower=True, including the
+        # '0th' derivative (the undifferentiated function).
+        # E.g. to evaluate the 5th derivative alone, call
+        # _evaluate_derivatives(x, der=6, all_lower=False).
+
+        if (not all_lower) and (x.size == 0 or self.r == 0):
+            return np.zeros((0, self.r), dtype=self.dtype)
+
+        if (not all_lower) and der == 1:
+            return self._evaluate(x)
+
+        if (not all_lower) and (der > self.n):
+            return np.zeros((len(x), self.r), dtype=self.dtype)
+
+        if der is None:
+            der = self.n
+
+        if all_lower and (x.size == 0 or self.r == 0):
+            return np.zeros((der, len(x), self.r), dtype=self.dtype)
+
+        if self._diff_cij is None:
+            # c[i,j] = xi[i] - xi[j]
+            c = self.xi[:, np.newaxis] - self.xi
+
+            # avoid division by 0 (diagonal entries are so far zero by construction)
+            np.fill_diagonal(c, 1)
+
+            # c[i,j] = (w[j] / w[i]) / (xi[i] - xi[j]) (equation 9.4)
+            c = self.wi/ (c * self.wi[..., np.newaxis])
+
+            # fill in correct diagonal entries: each column sums to 0
+            np.fill_diagonal(c, 0)
+
+            # calculate diagonal
+            # c[j,j] = -sum_{i != j} c[i,j] (equation 9.5)
+            d = -c.sum(axis=1)
+            # c[i,j] = l_j(x_i)
+            np.fill_diagonal(c, d)
+
+            self._diff_cij = c
+
+        if self._diff_baryint is None:
+            # initialise and cache derivative interpolator and cijs;
+            # reuse weights wi (which depend only on interpolation points xi),
+            # to avoid unnecessary re-computation
+            self._diff_baryint = BarycentricInterpolator(xi=self.xi,
+                                                         yi=self._diff_cij @ self.yi,
+                                                         wi=self.wi)
+            self._diff_baryint._diff_cij = self._diff_cij
+
+        if all_lower:
+            # assemble matrix of derivatives from order 0 to order der-1,
+            # in the format required by _Interpolator1DWithDerivatives.
+            cn = np.zeros((der, len(x), self.r), dtype=self.dtype)
+            for d in range(der):
+                cn[d, :, :] = self._evaluate_derivatives(x, d+1, all_lower=False)
+            return cn
+
+        # recursively evaluate only the derivative requested
+        return self._diff_baryint._evaluate_derivatives(x, der-1, all_lower=False)
+
+
+def barycentric_interpolate(xi, yi, x, axis=0, *, der=0):
+    """
+    Convenience function for polynomial interpolation.
+
+    Constructs a polynomial that passes through a given set of points,
+    then evaluates the polynomial. For reasons of numerical stability,
+    this function does not compute the coefficients of the polynomial.
+
+    This function uses a "barycentric interpolation" method that treats
+    the problem as a special case of rational function interpolation.
+    This algorithm is quite stable, numerically, but even in a world of
+    exact computation, unless the `x` coordinates are chosen very
+    carefully - Chebyshev zeros (e.g., cos(i*pi/n)) are a good choice -
+    polynomial interpolation itself is a very ill-conditioned process
+    due to the Runge phenomenon.
+
+    Parameters
+    ----------
+    xi : array_like
+        1-D array of x coordinates of the points the polynomial should
+        pass through
+    yi : array_like
+        The y coordinates of the points the polynomial should pass through.
+    x : scalar or array_like
+        Point or points at which to evaluate the interpolant.
+    der : int or list or None, optional
+        How many derivatives to evaluate, or None for all potentially
+        nonzero derivatives (that is, a number equal to the number
+        of points), or a list of derivatives to evaluate. This number
+        includes the function value as the '0th' derivative.
+    axis : int, optional
+        Axis in the `yi` array corresponding to the x-coordinate values.
+
+    Returns
+    -------
+    y : scalar or array_like
+        Interpolated values. Shape is determined by replacing
+        the interpolation axis in the original array with the shape of `x`.
+
+    See Also
+    --------
+    BarycentricInterpolator : Barycentric interpolator
+
+    Notes
+    -----
+    Construction of the interpolation weights is a relatively slow process.
+    If you want to call this many times with the same xi (but possibly
+    varying yi or x) you should use the class `BarycentricInterpolator`.
+    This is what this function uses internally.
+
+    Examples
+    --------
+    We can interpolate 2D observed data using barycentric interpolation:
+
+    >>> import numpy as np
+    >>> import matplotlib.pyplot as plt
+    >>> from scipy.interpolate import barycentric_interpolate
+    >>> x_observed = np.linspace(0.0, 10.0, 11)
+    >>> y_observed = np.sin(x_observed)
+    >>> x = np.linspace(min(x_observed), max(x_observed), num=100)
+    >>> y = barycentric_interpolate(x_observed, y_observed, x)
+    >>> plt.plot(x_observed, y_observed, "o", label="observation")
+    >>> plt.plot(x, y, label="barycentric interpolation")
+    >>> plt.legend()
+    >>> plt.show()
+
+    """
+    P = BarycentricInterpolator(xi, yi, axis=axis)
+    if der == 0:
+        return P(x)
+    elif _isscalar(der):
+        return P.derivative(x, der=der)
+    else:
+        return P.derivatives(x, der=np.amax(der)+1)[der]

venv/lib/python3.10/site-packages/scipy/interpolate/_rbf.py

@@ -0,0 +1,290 @@
+"""rbf - Radial basis functions for interpolation/smoothing scattered N-D data.
+
+Written by John Travers <[email protected]>, February 2007
+Based closely on Matlab code by Alex Chirokov
+Additional, large, improvements by Robert Hetland
+Some additional alterations by Travis Oliphant
+Interpolation with multi-dimensional target domain by Josua Sassen
+
+Permission to use, modify, and distribute this software is given under the
+terms of the SciPy (BSD style) license. See LICENSE.txt that came with
+this distribution for specifics.
+
+NO WARRANTY IS EXPRESSED OR IMPLIED. USE AT YOUR OWN RISK.
+
+Copyright (c) 2006-2007, Robert Hetland <[email protected]>
+Copyright (c) 2007, John Travers <[email protected]>
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+    * Redistributions of source code must retain the above copyright
+       notice, this list of conditions and the following disclaimer.
+
+    * Redistributions in binary form must reproduce the above
+       copyright notice, this list of conditions and the following
+       disclaimer in the documentation and/or other materials provided
+       with the distribution.
+
+    * Neither the name of Robert Hetland nor the names of any
+       contributors may be used to endorse or promote products derived
+       from this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+"""
+import numpy as np
+
+from scipy import linalg
+from scipy.special import xlogy
+from scipy.spatial.distance import cdist, pdist, squareform
+
+__all__ = ['Rbf']
+
+
+class Rbf:
+    """
+    Rbf(*args, **kwargs)
+
+    A class for radial basis function interpolation of functions from
+    N-D scattered data to an M-D domain.
+
+    .. legacy:: class
+
+        `Rbf` is legacy code, for new usage please use `RBFInterpolator`
+        instead.
+
+    Parameters
+    ----------
+    *args : arrays
+        x, y, z, ..., d, where x, y, z, ... are the coordinates of the nodes
+        and d is the array of values at the nodes
+    function : str or callable, optional
+        The radial basis function, based on the radius, r, given by the norm
+        (default is Euclidean distance); the default is 'multiquadric'::
+
+            'multiquadric': sqrt((r/self.epsilon)**2 + 1)
+            'inverse': 1.0/sqrt((r/self.epsilon)**2 + 1)
+            'gaussian': exp(-(r/self.epsilon)**2)
+            'linear': r
+            'cubic': r**3
+            'quintic': r**5
+            'thin_plate': r**2 * log(r)
+
+        If callable, then it must take 2 arguments (self, r). The epsilon
+        parameter will be available as self.epsilon. Other keyword
+        arguments passed in will be available as well.
+
+    epsilon : float, optional
+        Adjustable constant for gaussian or multiquadrics functions
+        - defaults to approximate average distance between nodes (which is
+        a good start).
+    smooth : float, optional
+        Values greater than zero increase the smoothness of the
+        approximation. 0 is for interpolation (default), the function will
+        always go through the nodal points in this case.
+    norm : str, callable, optional
+        A function that returns the 'distance' between two points, with
+        inputs as arrays of positions (x, y, z, ...), and an output as an
+        array of distance. E.g., the default: 'euclidean', such that the result
+        is a matrix of the distances from each point in ``x1`` to each point in
+        ``x2``. For more options, see documentation of
+        `scipy.spatial.distances.cdist`.
+    mode : str, optional
+        Mode of the interpolation, can be '1-D' (default) or 'N-D'. When it is
+        '1-D' the data `d` will be considered as 1-D and flattened
+        internally. When it is 'N-D' the data `d` is assumed to be an array of
+        shape (n_samples, m), where m is the dimension of the target domain.
+
+
+    Attributes
+    ----------
+    N : int
+        The number of data points (as determined by the input arrays).
+    di : ndarray
+        The 1-D array of data values at each of the data coordinates `xi`.
+    xi : ndarray
+        The 2-D array of data coordinates.
+    function : str or callable
+        The radial basis function. See description under Parameters.
+    epsilon : float
+        Parameter used by gaussian or multiquadrics functions. See Parameters.
+    smooth : float
+        Smoothing parameter. See description under Parameters.
+    norm : str or callable
+        The distance function. See description under Parameters.
+    mode : str
+        Mode of the interpolation. See description under Parameters.
+    nodes : ndarray
+        A 1-D array of node values for the interpolation.
+    A : internal property, do not use
+
+    See Also
+    --------
+    RBFInterpolator
+
+    Examples
+    --------
+    >>> import numpy as np
+    >>> from scipy.interpolate import Rbf
+    >>> rng = np.random.default_rng()
+    >>> x, y, z, d = rng.random((4, 50))
+    >>> rbfi = Rbf(x, y, z, d)  # radial basis function interpolator instance
+    >>> xi = yi = zi = np.linspace(0, 1, 20)
+    >>> di = rbfi(xi, yi, zi)   # interpolated values
+    >>> di.shape
+    (20,)
+
+    """
+    # Available radial basis functions that can be selected as strings;
+    # they all start with _h_ (self._init_function relies on that)
+    def _h_multiquadric(self, r):
+        return np.sqrt((1.0/self.epsilon*r)**2 + 1)
+
+    def _h_inverse_multiquadric(self, r):
+        return 1.0/np.sqrt((1.0/self.epsilon*r)**2 + 1)
+
+    def _h_gaussian(self, r):
+        return np.exp(-(1.0/self.epsilon*r)**2)
+
+    def _h_linear(self, r):
+        return r
+
+    def _h_cubic(self, r):
+        return r**3
+
+    def _h_quintic(self, r):
+        return r**5
+
+    def _h_thin_plate(self, r):
+        return xlogy(r**2, r)
+
+    # Setup self._function and do smoke test on initial r
+    def _init_function(self, r):
+        if isinstance(self.function, str):
+            self.function = self.function.lower()
+            _mapped = {'inverse': 'inverse_multiquadric',
+                       'inverse multiquadric': 'inverse_multiquadric',
+                       'thin-plate': 'thin_plate'}
+            if self.function in _mapped:
+                self.function = _mapped[self.function]
+
+            func_name = "_h_" + self.function
+            if hasattr(self, func_name):
+                self._function = getattr(self, func_name)
+            else:
+                functionlist = [x[3:] for x in dir(self)
+                                if x.startswith('_h_')]
+                raise ValueError("function must be a callable or one of " +
+                                 ", ".join(functionlist))
+            self._function = getattr(self, "_h_"+self.function)
+        elif callable(self.function):
+            allow_one = False
+            if hasattr(self.function, 'func_code') or \
+               hasattr(self.function, '__code__'):
+                val = self.function
+                allow_one = True
+            elif hasattr(self.function, "__call__"):
+                val = self.function.__call__.__func__
+            else:
+                raise ValueError("Cannot determine number of arguments to "
+                                 "function")
+
+            argcount = val.__code__.co_argcount
+            if allow_one and argcount == 1:
+                self._function = self.function
+            elif argcount == 2:
+                self._function = self.function.__get__(self, Rbf)
+            else:
+                raise ValueError("Function argument must take 1 or 2 "
+                                 "arguments.")
+
+        a0 = self._function(r)
+        if a0.shape != r.shape:
+            raise ValueError("Callable must take array and return array of "
+                             "the same shape")
+        return a0
+
+    def __init__(self, *args, **kwargs):
+        # `args` can be a variable number of arrays; we flatten them and store
+        # them as a single 2-D array `xi` of shape (n_args-1, array_size),
+        # plus a 1-D array `di` for the values.
+        # All arrays must have the same number of elements
+        self.xi = np.asarray([np.asarray(a, dtype=np.float64).flatten()
+                              for a in args[:-1]])
+        self.N = self.xi.shape[-1]
+
+        self.mode = kwargs.pop('mode', '1-D')
+
+        if self.mode == '1-D':
+            self.di = np.asarray(args[-1]).flatten()
+            self._target_dim = 1
+        elif self.mode == 'N-D':
+            self.di = np.asarray(args[-1])
+            self._target_dim = self.di.shape[-1]
+        else:
+            raise ValueError("Mode has to be 1-D or N-D.")
+
+        if not all([x.size == self.di.shape[0] for x in self.xi]):
+            raise ValueError("All arrays must be equal length.")
+
+        self.norm = kwargs.pop('norm', 'euclidean')
+        self.epsilon = kwargs.pop('epsilon', None)
+        if self.epsilon is None:
+            # default epsilon is the "the average distance between nodes" based
+            # on a bounding hypercube
+            ximax = np.amax(self.xi, axis=1)
+            ximin = np.amin(self.xi, axis=1)
+            edges = ximax - ximin
+            edges = edges[np.nonzero(edges)]
+            self.epsilon = np.power(np.prod(edges)/self.N, 1.0/edges.size)
+
+        self.smooth = kwargs.pop('smooth', 0.0)
+        self.function = kwargs.pop('function', 'multiquadric')
+
+        # attach anything left in kwargs to self for use by any user-callable
+        # function or to save on the object returned.
+        for item, value in kwargs.items():
+            setattr(self, item, value)
+
+        # Compute weights
+        if self._target_dim > 1:  # If we have more than one target dimension,
+            # we first factorize the matrix
+            self.nodes = np.zeros((self.N, self._target_dim), dtype=self.di.dtype)
+            lu, piv = linalg.lu_factor(self.A)
+            for i in range(self._target_dim):
+                self.nodes[:, i] = linalg.lu_solve((lu, piv), self.di[:, i])
+        else:
+            self.nodes = linalg.solve(self.A, self.di)
+
+    @property
+    def A(self):
+        # this only exists for backwards compatibility: self.A was available
+        # and, at least technically, public.
+        r = squareform(pdist(self.xi.T, self.norm))  # Pairwise norm
+        return self._init_function(r) - np.eye(self.N)*self.smooth
+
+    def _call_norm(self, x1, x2):
+        return cdist(x1.T, x2.T, self.norm)
+
+    def __call__(self, *args):
+        args = [np.asarray(x) for x in args]
+        if not all([x.shape == y.shape for x in args for y in args]):
+            raise ValueError("Array lengths must be equal")
+        if self._target_dim > 1:
+            shp = args[0].shape + (self._target_dim,)
+        else:
+            shp = args[0].shape
+        xa = np.asarray([a.flatten() for a in args], dtype=np.float64)
+        r = self._call_norm(xa, self.xi)
+        return np.dot(self._function(r), self.nodes).reshape(shp)

venv/lib/python3.10/site-packages/scipy/interpolate/_rbfinterp.py

@@ -0,0 +1,550 @@
+"""Module for RBF interpolation."""
+import warnings
+from itertools import combinations_with_replacement
+
+import numpy as np
+from numpy.linalg import LinAlgError
+from scipy.spatial import KDTree
+from scipy.special import comb
+from scipy.linalg.lapack import dgesv  # type: ignore[attr-defined]
+
+from ._rbfinterp_pythran import (_build_system,
+                                 _build_evaluation_coefficients,
+                                 _polynomial_matrix)
+
+
+__all__ = ["RBFInterpolator"]
+
+
+# These RBFs are implemented.
+_AVAILABLE = {
+    "linear",
+    "thin_plate_spline",
+    "cubic",
+    "quintic",
+    "multiquadric",
+    "inverse_multiquadric",
+    "inverse_quadratic",
+    "gaussian"
+    }
+
+
+# The shape parameter does not need to be specified when using these RBFs.
+_SCALE_INVARIANT = {"linear", "thin_plate_spline", "cubic", "quintic"}
+
+
+# For RBFs that are conditionally positive definite of order m, the interpolant
+# should include polynomial terms with degree >= m - 1. Define the minimum
+# degrees here. These values are from Chapter 8 of Fasshauer's "Meshfree
+# Approximation Methods with MATLAB". The RBFs that are not in this dictionary
+# are positive definite and do not need polynomial terms.
+_NAME_TO_MIN_DEGREE = {
+    "multiquadric": 0,
+    "linear": 0,
+    "thin_plate_spline": 1,
+    "cubic": 1,
+    "quintic": 2
+    }
+
+
+def _monomial_powers(ndim, degree):
+    """Return the powers for each monomial in a polynomial.
+
+    Parameters
+    ----------
+    ndim : int
+        Number of variables in the polynomial.
+    degree : int
+        Degree of the polynomial.
+
+    Returns
+    -------
+    (nmonos, ndim) int ndarray
+        Array where each row contains the powers for each variable in a
+        monomial.
+
+    """
+    nmonos = comb(degree + ndim, ndim, exact=True)
+    out = np.zeros((nmonos, ndim), dtype=np.dtype("long"))
+    count = 0
+    for deg in range(degree + 1):
+        for mono in combinations_with_replacement(range(ndim), deg):
+            # `mono` is a tuple of variables in the current monomial with
+            # multiplicity indicating power (e.g., (0, 1, 1) represents x*y**2)
+            for var in mono:
+                out[count, var] += 1
+
+            count += 1
+
+    return out
+
+
+def _build_and_solve_system(y, d, smoothing, kernel, epsilon, powers):
+    """Build and solve the RBF interpolation system of equations.
+
+    Parameters
+    ----------
+    y : (P, N) float ndarray
+        Data point coordinates.
+    d : (P, S) float ndarray
+        Data values at `y`.
+    smoothing : (P,) float ndarray
+        Smoothing parameter for each data point.
+    kernel : str
+        Name of the RBF.
+    epsilon : float
+        Shape parameter.
+    powers : (R, N) int ndarray
+        The exponents for each monomial in the polynomial.
+
+    Returns
+    -------
+    coeffs : (P + R, S) float ndarray
+        Coefficients for each RBF and monomial.
+    shift : (N,) float ndarray
+        Domain shift used to create the polynomial matrix.
+    scale : (N,) float ndarray
+        Domain scaling used to create the polynomial matrix.
+
+    """
+    lhs, rhs, shift, scale = _build_system(
+        y, d, smoothing, kernel, epsilon, powers
+        )
+    _, _, coeffs, info = dgesv(lhs, rhs, overwrite_a=True, overwrite_b=True)
+    if info < 0:
+        raise ValueError(f"The {-info}-th argument had an illegal value.")
+    elif info > 0:
+        msg = "Singular matrix."
+        nmonos = powers.shape[0]
+        if nmonos > 0:
+            pmat = _polynomial_matrix((y - shift)/scale, powers)
+            rank = np.linalg.matrix_rank(pmat)
+            if rank < nmonos:
+                msg = (
+                    "Singular matrix. The matrix of monomials evaluated at "
+                    "the data point coordinates does not have full column "
+                    f"rank ({rank}/{nmonos})."
+                    )
+
+        raise LinAlgError(msg)
+
+    return shift, scale, coeffs
+
+
+class RBFInterpolator:
+    """Radial basis function (RBF) interpolation in N dimensions.
+
+    Parameters
+    ----------
+    y : (npoints, ndims) array_like
+        2-D array of data point coordinates.
+    d : (npoints, ...) array_like
+        N-D array of data values at `y`. The length of `d` along the first
+        axis must be equal to the length of `y`. Unlike some interpolators, the
+        interpolation axis cannot be changed.
+    neighbors : int, optional
+        If specified, the value of the interpolant at each evaluation point
+        will be computed using only this many nearest data points. All the data
+        points are used by default.
+    smoothing : float or (npoints, ) array_like, optional
+        Smoothing parameter. The interpolant perfectly fits the data when this
+        is set to 0. For large values, the interpolant approaches a least
+        squares fit of a polynomial with the specified degree. Default is 0.
+    kernel : str, optional
+        Type of RBF. This should be one of
+
+            - 'linear'               : ``-r``
+            - 'thin_plate_spline'    : ``r**2 * log(r)``
+            - 'cubic'                : ``r**3``
+            - 'quintic'              : ``-r**5``
+            - 'multiquadric'         : ``-sqrt(1 + r**2)``
+            - 'inverse_multiquadric' : ``1/sqrt(1 + r**2)``
+            - 'inverse_quadratic'    : ``1/(1 + r**2)``
+            - 'gaussian'             : ``exp(-r**2)``
+
+        Default is 'thin_plate_spline'.
+    epsilon : float, optional
+        Shape parameter that scales the input to the RBF. If `kernel` is
+        'linear', 'thin_plate_spline', 'cubic', or 'quintic', this defaults to
+        1 and can be ignored because it has the same effect as scaling the
+        smoothing parameter. Otherwise, this must be specified.
+    degree : int, optional
+        Degree of the added polynomial. For some RBFs the interpolant may not
+        be well-posed if the polynomial degree is too small. Those RBFs and
+        their corresponding minimum degrees are
+
+            - 'multiquadric'      : 0
+            - 'linear'            : 0
+            - 'thin_plate_spline' : 1
+            - 'cubic'             : 1
+            - 'quintic'           : 2
+
+        The default value is the minimum degree for `kernel` or 0 if there is
+        no minimum degree. Set this to -1 for no added polynomial.
+
+    Notes
+    -----
+    An RBF is a scalar valued function in N-dimensional space whose value at
+    :math:`x` can be expressed in terms of :math:`r=||x - c||`, where :math:`c`
+    is the center of the RBF.
+
+    An RBF interpolant for the vector of data values :math:`d`, which are from
+    locations :math:`y`, is a linear combination of RBFs centered at :math:`y`
+    plus a polynomial with a specified degree. The RBF interpolant is written
+    as
+
+    .. math::
+        f(x) = K(x, y) a + P(x) b,
+
+    where :math:`K(x, y)` is a matrix of RBFs with centers at :math:`y`
+    evaluated at the points :math:`x`, and :math:`P(x)` is a matrix of
+    monomials, which span polynomials with the specified degree, evaluated at
+    :math:`x`. The coefficients :math:`a` and :math:`b` are the solution to the
+    linear equations
+
+    .. math::
+        (K(y, y) + \\lambda I) a + P(y) b = d
+
+    and
+
+    .. math::
+        P(y)^T a = 0,
+
+    where :math:`\\lambda` is a non-negative smoothing parameter that controls
+    how well we want to fit the data. The data are fit exactly when the
+    smoothing parameter is 0.
+
+    The above system is uniquely solvable if the following requirements are
+    met:
+
+        - :math:`P(y)` must have full column rank. :math:`P(y)` always has full
+          column rank when `degree` is -1 or 0. When `degree` is 1,
+          :math:`P(y)` has full column rank if the data point locations are not
+          all collinear (N=2), coplanar (N=3), etc.
+        - If `kernel` is 'multiquadric', 'linear', 'thin_plate_spline',
+          'cubic', or 'quintic', then `degree` must not be lower than the
+          minimum value listed above.
+        - If `smoothing` is 0, then each data point location must be distinct.
+
+    When using an RBF that is not scale invariant ('multiquadric',
+    'inverse_multiquadric', 'inverse_quadratic', or 'gaussian'), an appropriate
+    shape parameter must be chosen (e.g., through cross validation). Smaller
+    values for the shape parameter correspond to wider RBFs. The problem can
+    become ill-conditioned or singular when the shape parameter is too small.
+
+    The memory required to solve for the RBF interpolation coefficients
+    increases quadratically with the number of data points, which can become
+    impractical when interpolating more than about a thousand data points.
+    To overcome memory limitations for large interpolation problems, the
+    `neighbors` argument can be specified to compute an RBF interpolant for
+    each evaluation point using only the nearest data points.
+
+    .. versionadded:: 1.7.0
+
+    See Also
+    --------
+    NearestNDInterpolator
+    LinearNDInterpolator
+    CloughTocher2DInterpolator
+
+    References
+    ----------
+    .. [1] Fasshauer, G., 2007. Meshfree Approximation Methods with Matlab.
+        World Scientific Publishing Co.
+
+    .. [2] http://amadeus.math.iit.edu/~fass/603_ch3.pdf
+
+    .. [3] Wahba, G., 1990. Spline Models for Observational Data. SIAM.
+
+    .. [4] http://pages.stat.wisc.edu/~wahba/stat860public/lect/lect8/lect8.pdf
+
+    Examples
+    --------
+    Demonstrate interpolating scattered data to a grid in 2-D.
+
+    >>> import numpy as np
+    >>> import matplotlib.pyplot as plt
+    >>> from scipy.interpolate import RBFInterpolator
+    >>> from scipy.stats.qmc import Halton
+
+    >>> rng = np.random.default_rng()
+    >>> xobs = 2*Halton(2, seed=rng).random(100) - 1
+    >>> yobs = np.sum(xobs, axis=1)*np.exp(-6*np.sum(xobs**2, axis=1))
+
+    >>> xgrid = np.mgrid[-1:1:50j, -1:1:50j]
+    >>> xflat = xgrid.reshape(2, -1).T
+    >>> yflat = RBFInterpolator(xobs, yobs)(xflat)
+    >>> ygrid = yflat.reshape(50, 50)
+
+    >>> fig, ax = plt.subplots()
+    >>> ax.pcolormesh(*xgrid, ygrid, vmin=-0.25, vmax=0.25, shading='gouraud')
+    >>> p = ax.scatter(*xobs.T, c=yobs, s=50, ec='k', vmin=-0.25, vmax=0.25)
+    >>> fig.colorbar(p)
+    >>> plt.show()
+
+    """
+
+    def __init__(self, y, d,
+                 neighbors=None,
+                 smoothing=0.0,
+                 kernel="thin_plate_spline",
+                 epsilon=None,
+                 degree=None):
+        y = np.asarray(y, dtype=float, order="C")
+        if y.ndim != 2:
+            raise ValueError("`y` must be a 2-dimensional array.")
+
+        ny, ndim = y.shape
+
+        d_dtype = complex if np.iscomplexobj(d) else float
+        d = np.asarray(d, dtype=d_dtype, order="C")
+        if d.shape[0] != ny:
+            raise ValueError(
+                f"Expected the first axis of `d` to have length {ny}."
+                )
+
+        d_shape = d.shape[1:]
+        d = d.reshape((ny, -1))
+        # If `d` is complex, convert it to a float array with twice as many
+        # columns. Otherwise, the LHS matrix would need to be converted to
+        # complex and take up 2x more memory than necessary.
+        d = d.view(float)
+
+        if np.isscalar(smoothing):
+            smoothing = np.full(ny, smoothing, dtype=float)
+        else:
+            smoothing = np.asarray(smoothing, dtype=float, order="C")
+            if smoothing.shape != (ny,):
+                raise ValueError(
+                    "Expected `smoothing` to be a scalar or have shape "
+                    f"({ny},)."
+                    )
+
+        kernel = kernel.lower()
+        if kernel not in _AVAILABLE:
+            raise ValueError(f"`kernel` must be one of {_AVAILABLE}.")
+
+        if epsilon is None:
+            if kernel in _SCALE_INVARIANT:
+                epsilon = 1.0
+            else:
+                raise ValueError(
+                    "`epsilon` must be specified if `kernel` is not one of "
+                    f"{_SCALE_INVARIANT}."
+                    )
+        else:
+            epsilon = float(epsilon)
+
+        min_degree = _NAME_TO_MIN_DEGREE.get(kernel, -1)
+        if degree is None:
+            degree = max(min_degree, 0)
+        else:
+            degree = int(degree)
+            if degree < -1:
+                raise ValueError("`degree` must be at least -1.")
+            elif -1 < degree < min_degree:
+                warnings.warn(
+                    f"`degree` should not be below {min_degree} except -1 "
+                    f"when `kernel` is '{kernel}'."
+                    f"The interpolant may not be uniquely "
+                    f"solvable, and the smoothing parameter may have an "
+                    f"unintuitive effect.",
+                    UserWarning, stacklevel=2
+                )
+
+        if neighbors is None:
+            nobs = ny
+        else:
+            # Make sure the number of nearest neighbors used for interpolation
+            # does not exceed the number of observations.
+            neighbors = int(min(neighbors, ny))
+            nobs = neighbors
+
+        powers = _monomial_powers(ndim, degree)
+        # The polynomial matrix must have full column rank in order for the
+        # interpolant to be well-posed, which is not possible if there are
+        # fewer observations than monomials.
+        if powers.shape[0] > nobs:
+            raise ValueError(
+                f"At least {powers.shape[0]} data points are required when "
+                f"`degree` is {degree} and the number of dimensions is {ndim}."
+                )
+
+        if neighbors is None:
+            shift, scale, coeffs = _build_and_solve_system(
+                y, d, smoothing, kernel, epsilon, powers
+                )
+
+            # Make these attributes private since they do not always exist.
+            self._shift = shift
+            self._scale = scale
+            self._coeffs = coeffs
+
+        else:
+            self._tree = KDTree(y)
+
+        self.y = y
+        self.d = d
+        self.d_shape = d_shape
+        self.d_dtype = d_dtype
+        self.neighbors = neighbors
+        self.smoothing = smoothing
+        self.kernel = kernel
+        self.epsilon = epsilon
+        self.powers = powers
+
+    def _chunk_evaluator(
+            self,
+            x,
+            y,
+            shift,
+            scale,
+            coeffs,
+            memory_budget=1000000
+    ):
+        """
+        Evaluate the interpolation while controlling memory consumption.
+        We chunk the input if we need more memory than specified.
+
+        Parameters
+        ----------
+        x : (Q, N) float ndarray
+            array of points on which to evaluate
+        y: (P, N) float ndarray
+            array of points on which we know function values
+        shift: (N, ) ndarray
+            Domain shift used to create the polynomial matrix.
+        scale : (N,) float ndarray
+            Domain scaling used to create the polynomial matrix.
+        coeffs: (P+R, S) float ndarray
+            Coefficients in front of basis functions
+        memory_budget: int
+            Total amount of memory (in units of sizeof(float)) we wish
+            to devote for storing the array of coefficients for
+            interpolated points. If we need more memory than that, we
+            chunk the input.
+
+        Returns
+        -------
+        (Q, S) float ndarray
+        Interpolated array
+        """
+        nx, ndim = x.shape
+        if self.neighbors is None:
+            nnei = len(y)
+        else:
+            nnei = self.neighbors
+        # in each chunk we consume the same space we already occupy
+        chunksize = memory_budget // (self.powers.shape[0] + nnei) + 1
+        if chunksize <= nx:
+            out = np.empty((nx, self.d.shape[1]), dtype=float)
+            for i in range(0, nx, chunksize):
+                vec = _build_evaluation_coefficients(
+                    x[i:i + chunksize, :],
+                    y,
+                    self.kernel,
+                    self.epsilon,
+                    self.powers,
+                    shift,
+                    scale)
+                out[i:i + chunksize, :] = np.dot(vec, coeffs)
+        else:
+            vec = _build_evaluation_coefficients(
+                x,
+                y,
+                self.kernel,
+                self.epsilon,
+                self.powers,
+                shift,
+                scale)
+            out = np.dot(vec, coeffs)
+        return out
+
+    def __call__(self, x):
+        """Evaluate the interpolant at `x`.
+
+        Parameters
+        ----------
+        x : (Q, N) array_like
+            Evaluation point coordinates.
+
+        Returns
+        -------
+        (Q, ...) ndarray
+            Values of the interpolant at `x`.
+
+        """
+        x = np.asarray(x, dtype=float, order="C")
+        if x.ndim != 2:
+            raise ValueError("`x` must be a 2-dimensional array.")
+
+        nx, ndim = x.shape
+        if ndim != self.y.shape[1]:
+            raise ValueError("Expected the second axis of `x` to have length "
+                             f"{self.y.shape[1]}.")
+
+        # Our memory budget for storing RBF coefficients is
+        # based on how many floats in memory we already occupy
+        # If this number is below 1e6 we just use 1e6
+        # This memory budget is used to decide how we chunk
+        # the inputs
+        memory_budget = max(x.size + self.y.size + self.d.size, 1000000)
+
+        if self.neighbors is None:
+            out = self._chunk_evaluator(
+                x,
+                self.y,
+                self._shift,
+                self._scale,
+                self._coeffs,
+                memory_budget=memory_budget)
+        else:
+            # Get the indices of the k nearest observation points to each
+            # evaluation point.
+            _, yindices = self._tree.query(x, self.neighbors)
+            if self.neighbors == 1:
+                # `KDTree` squeezes the output when neighbors=1.
+                yindices = yindices[:, None]
+
+            # Multiple evaluation points may have the same neighborhood of
+            # observation points. Make the neighborhoods unique so that we only
+            # compute the interpolation coefficients once for each
+            # neighborhood.
+            yindices = np.sort(yindices, axis=1)
+            yindices, inv = np.unique(yindices, return_inverse=True, axis=0)
+            inv = np.reshape(inv, (-1,))  # flatten, we need 1-D indices
+            # `inv` tells us which neighborhood will be used by each evaluation
+            # point. Now we find which evaluation points will be using each
+            # neighborhood.
+            xindices = [[] for _ in range(len(yindices))]
+            for i, j in enumerate(inv):
+                xindices[j].append(i)
+
+            out = np.empty((nx, self.d.shape[1]), dtype=float)
+            for xidx, yidx in zip(xindices, yindices):
+                # `yidx` are the indices of the observations in this
+                # neighborhood. `xidx` are the indices of the evaluation points
+                # that are using this neighborhood.
+                xnbr = x[xidx]
+                ynbr = self.y[yidx]
+                dnbr = self.d[yidx]
+                snbr = self.smoothing[yidx]
+                shift, scale, coeffs = _build_and_solve_system(
+                    ynbr,
+                    dnbr,
+                    snbr,
+                    self.kernel,
+                    self.epsilon,
+                    self.powers,
+                )
+                out[xidx] = self._chunk_evaluator(
+                    xnbr,
+                    ynbr,
+                    shift,
+                    scale,
+                    coeffs,
+                    memory_budget=memory_budget)
+
+        out = out.view(self.d_dtype)
+        out = out.reshape((nx, ) + self.d_shape)
+        return out