module documentation

Basic functions for manipulating 2d arrays
Variable array​_function​_dispatch Undocumented
Variable i1 Undocumented
Variable i2 Undocumented
Variable i4 Undocumented
Function ​_diag​_dispatcher Undocumented
Function ​_eye​_dispatcher Undocumented
Function ​_flip​_dispatcher Undocumented
Function ​_histogram2d​_dispatcher Undocumented
Function ​_min​_int get small int that fits the range
Function ​_tri​_dispatcher Undocumented
Function ​_trilu​_dispatcher Undocumented
Function ​_trilu​_indices​_form​_dispatcher Undocumented
Function ​_vander​_dispatcher Undocumented
Function diag Extract a diagonal or construct a diagonal array.
Function diagflat Create a two-dimensional array with the flattened input as a diagonal.
Function eye Return a 2-D array with ones on the diagonal and zeros elsewhere.
Function fliplr Reverse the order of elements along axis 1 (left/right).
Function flipud Reverse the order of elements along axis 0 (up/down).
Function histogram2d Compute the bi-dimensional histogram of two data samples.
Function mask​_indices Return the indices to access (n, n) arrays, given a masking function.
Function tri An array with ones at and below the given diagonal and zeros elsewhere.
Function tril Lower triangle of an array.
Function tril​_indices Return the indices for the lower-triangle of an (n, m) array.
Function tril​_indices​_from Return the indices for the lower-triangle of arr.
Function triu Upper triangle of an array.
Function triu​_indices Return the indices for the upper-triangle of an (n, m) array.
Function triu​_indices​_from Return the indices for the upper-triangle of arr.
Function vander Generate a Vandermonde matrix.
Variable ​_eye​_with​_like Undocumented
Variable ​_tri​_with​_like Undocumented
array_function_dispatch =

Undocumented

i1 =

Undocumented

i2 =

Undocumented

i4 =

Undocumented

def _diag_dispatcher(v, k=None):

Undocumented

def _eye_dispatcher(N, M=None, k=None, dtype=None, order=None, *, like=None):

Undocumented

def _flip_dispatcher(m):

Undocumented

def _histogram2d_dispatcher(x, y, bins=None, range=None, normed=None, weights=None, density=None):

Undocumented

def _min_int(low, high):
get small int that fits the range
def _tri_dispatcher(N, M=None, k=None, dtype=None, *, like=None):

Undocumented

def _trilu_dispatcher(m, k=None):

Undocumented

def _trilu_indices_form_dispatcher(arr, k=None):

Undocumented

def _vander_dispatcher(x, N=None, increasing=None):

Undocumented

Extract a diagonal or construct a diagonal array.

See the more detailed documentation for numpy.diagonal if you use this function to extract a diagonal and wish to write to the resulting array; whether it returns a copy or a view depends on what version of numpy you are using.

Parameters

v : array_like
If v is a 2-D array, return a copy of its k-th diagonal. If v is a 1-D array, return a 2-D array with v on the k-th diagonal.
k : int, optional
Diagonal in question. The default is 0. Use k>0 for diagonals above the main diagonal, and k<0 for diagonals below the main diagonal.

Returns

out : ndarray
The extracted diagonal or constructed diagonal array.

See Also

diagonal : Return specified diagonals. diagflat : Create a 2-D array with the flattened input as a diagonal. trace : Sum along diagonals. triu : Upper triangle of an array. tril : Lower triangle of an array.

Examples

>>> x = np.arange(9).reshape((3,3))
>>> x
array([[0, 1, 2],
       [3, 4, 5],
       [6, 7, 8]])
>>> np.diag(x)
array([0, 4, 8])
>>> np.diag(x, k=1)
array([1, 5])
>>> np.diag(x, k=-1)
array([3, 7])
>>> np.diag(np.diag(x))
array([[0, 0, 0],
       [0, 4, 0],
       [0, 0, 8]])
@array_function_dispatch(_diag_dispatcher)
def diagflat(v, k=0):

Create a two-dimensional array with the flattened input as a diagonal.

Parameters

v : array_like
Input data, which is flattened and set as the k-th diagonal of the output.
k : int, optional
Diagonal to set; 0, the default, corresponds to the "main" diagonal, a positive (negative) k giving the number of the diagonal above (below) the main.

Returns

out : ndarray
The 2-D output array.

See Also

diag : MATLAB work-alike for 1-D and 2-D arrays. diagonal : Return specified diagonals. trace : Sum along diagonals.

Examples

>>> np.diagflat([[1,2], [3,4]])
array([[1, 0, 0, 0],
       [0, 2, 0, 0],
       [0, 0, 3, 0],
       [0, 0, 0, 4]])
>>> np.diagflat([1,2], 1)
array([[0, 1, 0],
       [0, 0, 2],
       [0, 0, 0]])
@set_array_function_like_doc
@set_module('numpy')
def eye(N, M=None, k=0, dtype=float, order='C', *, like=None):

Return a 2-D array with ones on the diagonal and zeros elsewhere.

Parameters

N : int
Number of rows in the output.
M : int, optional
Number of columns in the output. If None, defaults to N.
k : int, optional
Index of the diagonal: 0 (the default) refers to the main diagonal, a positive value refers to an upper diagonal, and a negative value to a lower diagonal.
dtype : data-type, optional
Data-type of the returned array.
order : {'C', 'F'}, optional

Whether the output should be stored in row-major (C-style) or column-major (Fortran-style) order in memory.

New in version 1.14.0.

${ARRAY_FUNCTION_LIKE}

New in version 1.20.0.

Returns

I : ndarray of shape (N,M)
An array where all elements are equal to zero, except for the k-th diagonal, whose values are equal to one.

See Also

identity : (almost) equivalent function diag : diagonal 2-D array from a 1-D array specified by the user.

Examples

>>> np.eye(2, dtype=int)
array([[1, 0],
       [0, 1]])
>>> np.eye(3, k=1)
array([[0.,  1.,  0.],
       [0.,  0.,  1.],
       [0.,  0.,  0.]])

Reverse the order of elements along axis 1 (left/right).

For a 2-D array, this flips the entries in each row in the left/right direction. Columns are preserved, but appear in a different order than before.

Parameters

m : array_like
Input array, must be at least 2-D.

Returns

f : ndarray
A view of m with the columns reversed. Since a view is returned, this operation is O(1).

See Also

flipud : Flip array in the up/down direction. flip : Flip array in one or more dimensions. rot90 : Rotate array counterclockwise.

Notes

Equivalent to m[:,::-1] or np.flip(m, axis=1). Requires the array to be at least 2-D.

Examples

>>> A = np.diag([1.,2.,3.])
>>> A
array([[1.,  0.,  0.],
       [0.,  2.,  0.],
       [0.,  0.,  3.]])
>>> np.fliplr(A)
array([[0.,  0.,  1.],
       [0.,  2.,  0.],
       [3.,  0.,  0.]])
>>> A = np.random.randn(2,3,5)
>>> np.all(np.fliplr(A) == A[:,::-1,...])
True

Reverse the order of elements along axis 0 (up/down).

For a 2-D array, this flips the entries in each column in the up/down direction. Rows are preserved, but appear in a different order than before.

Parameters

m : array_like
Input array.

Returns

out : array_like
A view of m with the rows reversed. Since a view is returned, this operation is O(1).

See Also

fliplr : Flip array in the left/right direction. flip : Flip array in one or more dimensions. rot90 : Rotate array counterclockwise.

Notes

Equivalent to m[::-1, ...] or np.flip(m, axis=0). Requires the array to be at least 1-D.

Examples

>>> A = np.diag([1.0, 2, 3])
>>> A
array([[1.,  0.,  0.],
       [0.,  2.,  0.],
       [0.,  0.,  3.]])
>>> np.flipud(A)
array([[0.,  0.,  3.],
       [0.,  2.,  0.],
       [1.,  0.,  0.]])
>>> A = np.random.randn(2,3,5)
>>> np.all(np.flipud(A) == A[::-1,...])
True
>>> np.flipud([1,2])
array([2, 1])
@array_function_dispatch(_histogram2d_dispatcher)
def histogram2d(x, y, bins=10, range=None, normed=None, weights=None, density=None):

Compute the bi-dimensional histogram of two data samples.

Parameters

x : array_like, shape (N,)
An array containing the x coordinates of the points to be histogrammed.
y : array_like, shape (N,)
An array containing the y coordinates of the points to be histogrammed.
bins : int or array_like or [int, int] or [array, array], optional

The bin specification:

  • If int, the number of bins for the two dimensions (nx=ny=bins).
  • If array_like, the bin edges for the two dimensions (x_edges=y_edges=bins).
  • If [int, int], the number of bins in each dimension (nx, ny = bins).
  • If [array, array], the bin edges in each dimension (x_edges, y_edges = bins).
  • A combination [int, array] or [array, int], where int is the number of bins and array is the bin edges.
range : array_like, shape(2,2), optional
The leftmost and rightmost edges of the bins along each dimension (if not specified explicitly in the bins parameters): [[xmin, xmax], [ymin, ymax]]. All values outside of this range will be considered outliers and not tallied in the histogram.
density : bool, optional
If False, the default, returns the number of samples in each bin. If True, returns the probability density function at the bin, bin_count / sample_count / bin_area.
normed : bool, optional
An alias for the density argument that behaves identically. To avoid confusion with the broken normed argument to histogram, density should be preferred.
weights : array_like, shape(N,), optional
An array of values w_i weighing each sample (x_i, y_i). Weights are normalized to 1 if normed is True. If normed is False, the values of the returned histogram are equal to the sum of the weights belonging to the samples falling into each bin.

Returns

H : ndarray, shape(nx, ny)
The bi-dimensional histogram of samples x and y. Values in x are histogrammed along the first dimension and values in y are histogrammed along the second dimension.
xedges : ndarray, shape(nx+1,)
The bin edges along the first dimension.
yedges : ndarray, shape(ny+1,)
The bin edges along the second dimension.

See Also

histogram : 1D histogram histogramdd : Multidimensional histogram

Notes

When normed is True, then the returned histogram is the sample density, defined such that the sum over bins of the product bin_value * bin_area is 1.

Please note that the histogram does not follow the Cartesian convention where x values are on the abscissa and y values on the ordinate axis. Rather, x is histogrammed along the first dimension of the array (vertical), and y along the second dimension of the array (horizontal). This ensures compatibility with histogramdd.

Examples

>>> from matplotlib.image import NonUniformImage
>>> import matplotlib.pyplot as plt

Construct a 2-D histogram with variable bin width. First define the bin edges:

>>> xedges = [0, 1, 3, 5]
>>> yedges = [0, 2, 3, 4, 6]

Next we create a histogram H with random bin content:

>>> x = np.random.normal(2, 1, 100)
>>> y = np.random.normal(1, 1, 100)
>>> H, xedges, yedges = np.histogram2d(x, y, bins=(xedges, yedges))
>>> # Histogram does not follow Cartesian convention (see Notes),
>>> # therefore transpose H for visualization purposes.
>>> H = H.T

imshow can only display square bins:

>>> fig = plt.figure(figsize=(7, 3))
>>> ax = fig.add_subplot(131, title='imshow: square bins')
>>> plt.imshow(H, interpolation='nearest', origin='lower',
...         extent=[xedges[0], xedges[-1], yedges[0], yedges[-1]])
<matplotlib.image.AxesImage object at 0x...>

pcolormesh can display actual edges:

>>> ax = fig.add_subplot(132, title='pcolormesh: actual edges',
...         aspect='equal')
>>> X, Y = np.meshgrid(xedges, yedges)
>>> ax.pcolormesh(X, Y, H)
<matplotlib.collections.QuadMesh object at 0x...>

NonUniformImage can be used to display actual bin edges with interpolation:

>>> ax = fig.add_subplot(133, title='NonUniformImage: interpolated',
...         aspect='equal', xlim=xedges[[0, -1]], ylim=yedges[[0, -1]])
>>> im = NonUniformImage(ax, interpolation='bilinear')
>>> xcenters = (xedges[:-1] + xedges[1:]) / 2
>>> ycenters = (yedges[:-1] + yedges[1:]) / 2
>>> im.set_data(xcenters, ycenters, H)
>>> ax.images.append(im)
>>> plt.show()

It is also possible to construct a 2-D histogram without specifying bin edges:

>>> # Generate non-symmetric test data
>>> n = 10000
>>> x = np.linspace(1, 100, n)
>>> y = 2*np.log(x) + np.random.rand(n) - 0.5
>>> # Compute 2d histogram. Note the order of x/y and xedges/yedges
>>> H, yedges, xedges = np.histogram2d(y, x, bins=20)

Now we can plot the histogram using pcolormesh, and a hexbin for comparison.

>>> # Plot histogram using pcolormesh
>>> fig, (ax1, ax2) = plt.subplots(ncols=2, sharey=True)
>>> ax1.pcolormesh(xedges, yedges, H, cmap='rainbow')
>>> ax1.plot(x, 2*np.log(x), 'k-')
>>> ax1.set_xlim(x.min(), x.max())
>>> ax1.set_ylim(y.min(), y.max())
>>> ax1.set_xlabel('x')
>>> ax1.set_ylabel('y')
>>> ax1.set_title('histogram2d')
>>> ax1.grid()
>>> # Create hexbin plot for comparison
>>> ax2.hexbin(x, y, gridsize=20, cmap='rainbow')
>>> ax2.plot(x, 2*np.log(x), 'k-')
>>> ax2.set_title('hexbin')
>>> ax2.set_xlim(x.min(), x.max())
>>> ax2.set_xlabel('x')
>>> ax2.grid()
>>> plt.show()
@set_module('numpy')
def mask_indices(n, mask_func, k=0):

Return the indices to access (n, n) arrays, given a masking function.

Assume mask_func is a function that, for a square array a of size (n, n) with a possible offset argument k, when called as mask_func(a, k) returns a new array with zeros in certain locations (functions like triu or tril do precisely this). Then this function returns the indices where the non-zero values would be located.

Parameters

n : int
The returned indices will be valid to access arrays of shape (n, n).
mask_func : callable
A function whose call signature is similar to that of triu, tril. That is, mask_func(x, k) returns a boolean array, shaped like x. k is an optional argument to the function.
k : scalar
An optional argument which is passed through to mask_func. Functions like triu, tril take a second argument that is interpreted as an offset.

Returns

indices : tuple of arrays.
The n arrays of indices corresponding to the locations where mask_func(np.ones((n, n)), k) is True.

See Also

triu, tril, triu_indices, tril_indices

Notes

New in version 1.4.0.

Examples

These are the indices that would allow you to access the upper triangular part of any 3x3 array:

>>> iu = np.mask_indices(3, np.triu)

For example, if a is a 3x3 array:

>>> a = np.arange(9).reshape(3, 3)
>>> a
array([[0, 1, 2],
       [3, 4, 5],
       [6, 7, 8]])
>>> a[iu]
array([0, 1, 2, 4, 5, 8])

An offset can be passed also to the masking function. This gets us the indices starting on the first diagonal right of the main one:

>>> iu1 = np.mask_indices(3, np.triu, 1)

with which we now extract only three elements:

>>> a[iu1]
array([1, 2, 5])
@set_array_function_like_doc
@set_module('numpy')
def tri(N, M=None, k=0, dtype=float, *, like=None):

An array with ones at and below the given diagonal and zeros elsewhere.

Parameters

N : int
Number of rows in the array.
M : int, optional
Number of columns in the array. By default, M is taken equal to N.
k : int, optional
The sub-diagonal at and below which the array is filled. k = 0 is the main diagonal, while k < 0 is below it, and k > 0 is above. The default is 0.
dtype : dtype, optional
Data type of the returned array. The default is float.

${ARRAY_FUNCTION_LIKE}

New in version 1.20.0.

Returns

tri : ndarray of shape (N, M)
Array with its lower triangle filled with ones and zero elsewhere; in other words T[i,j] == 1 for j <= i + k, 0 otherwise.

Examples

>>> np.tri(3, 5, 2, dtype=int)
array([[1, 1, 1, 0, 0],
       [1, 1, 1, 1, 0],
       [1, 1, 1, 1, 1]])
>>> np.tri(3, 5, -1)
array([[0.,  0.,  0.,  0.,  0.],
       [1.,  0.,  0.,  0.,  0.],
       [1.,  1.,  0.,  0.,  0.]])

Lower triangle of an array.

Return a copy of an array with elements above the k-th diagonal zeroed. For arrays with ndim exceeding 2, tril will apply to the final two axes.

Parameters

m : array_like, shape (..., M, N)
Input array.
k : int, optional
Diagonal above which to zero elements. k = 0 (the default) is the main diagonal, k < 0 is below it and k > 0 is above.

Returns

tril : ndarray, shape (..., M, N)
Lower triangle of m, of same shape and data-type as m.

See Also

triu : same thing, only for the upper triangle

Examples

>>> np.tril([[1,2,3],[4,5,6],[7,8,9],[10,11,12]], -1)
array([[ 0,  0,  0],
       [ 4,  0,  0],
       [ 7,  8,  0],
       [10, 11, 12]])
>>> np.tril(np.arange(3*4*5).reshape(3, 4, 5))
array([[[ 0,  0,  0,  0,  0],
        [ 5,  6,  0,  0,  0],
        [10, 11, 12,  0,  0],
        [15, 16, 17, 18,  0]],
       [[20,  0,  0,  0,  0],
        [25, 26,  0,  0,  0],
        [30, 31, 32,  0,  0],
        [35, 36, 37, 38,  0]],
       [[40,  0,  0,  0,  0],
        [45, 46,  0,  0,  0],
        [50, 51, 52,  0,  0],
        [55, 56, 57, 58,  0]]])
@set_module('numpy')
def tril_indices(n, k=0, m=None):

Return the indices for the lower-triangle of an (n, m) array.

Parameters

n : int
The row dimension of the arrays for which the returned indices will be valid.
k : int, optional
Diagonal offset (see tril for details).
m : int, optional
New in version 1.9.0.

The column dimension of the arrays for which the returned arrays will be valid. By default m is taken equal to n.

Returns

inds : tuple of arrays
The indices for the triangle. The returned tuple contains two arrays, each with the indices along one dimension of the array.

See also

triu_indices : similar function, for upper-triangular. mask_indices : generic function accepting an arbitrary mask function. tril, triu

Notes

New in version 1.4.0.

Examples

Compute two different sets of indices to access 4x4 arrays, one for the lower triangular part starting at the main diagonal, and one starting two diagonals further right:

>>> il1 = np.tril_indices(4)
>>> il2 = np.tril_indices(4, 2)

Here is how they can be used with a sample array:

>>> a = np.arange(16).reshape(4, 4)
>>> a
array([[ 0,  1,  2,  3],
       [ 4,  5,  6,  7],
       [ 8,  9, 10, 11],
       [12, 13, 14, 15]])

Both for indexing:

>>> a[il1]
array([ 0,  4,  5, ..., 13, 14, 15])

And for assigning values:

>>> a[il1] = -1
>>> a
array([[-1,  1,  2,  3],
       [-1, -1,  6,  7],
       [-1, -1, -1, 11],
       [-1, -1, -1, -1]])

These cover almost the whole array (two diagonals right of the main one):

>>> a[il2] = -10
>>> a
array([[-10, -10, -10,   3],
       [-10, -10, -10, -10],
       [-10, -10, -10, -10],
       [-10, -10, -10, -10]])
@array_function_dispatch(_trilu_indices_form_dispatcher)
def tril_indices_from(arr, k=0):

Return the indices for the lower-triangle of arr.

See tril_indices for full details.

Parameters

arr : array_like
The indices will be valid for square arrays whose dimensions are the same as arr.
k : int, optional
Diagonal offset (see tril for details).

See Also

tril_indices, tril

Notes

New in version 1.4.0.

Upper triangle of an array.

Return a copy of an array with the elements below the k-th diagonal zeroed. For arrays with ndim exceeding 2, triu will apply to the final two axes.

Please refer to the documentation for tril for further details.

See Also

tril : lower triangle of an array

Examples

>>> np.triu([[1,2,3],[4,5,6],[7,8,9],[10,11,12]], -1)
array([[ 1,  2,  3],
       [ 4,  5,  6],
       [ 0,  8,  9],
       [ 0,  0, 12]])
>>> np.triu(np.arange(3*4*5).reshape(3, 4, 5))
array([[[ 0,  1,  2,  3,  4],
        [ 0,  6,  7,  8,  9],
        [ 0,  0, 12, 13, 14],
        [ 0,  0,  0, 18, 19]],
       [[20, 21, 22, 23, 24],
        [ 0, 26, 27, 28, 29],
        [ 0,  0, 32, 33, 34],
        [ 0,  0,  0, 38, 39]],
       [[40, 41, 42, 43, 44],
        [ 0, 46, 47, 48, 49],
        [ 0,  0, 52, 53, 54],
        [ 0,  0,  0, 58, 59]]])
@set_module('numpy')
def triu_indices(n, k=0, m=None):

Return the indices for the upper-triangle of an (n, m) array.

Parameters

n : int
The size of the arrays for which the returned indices will be valid.
k : int, optional
Diagonal offset (see triu for details).
m : int, optional
New in version 1.9.0.

The column dimension of the arrays for which the returned arrays will be valid. By default m is taken equal to n.

Returns

inds : tuple, shape(2) of ndarrays, shape(n)
The indices for the triangle. The returned tuple contains two arrays, each with the indices along one dimension of the array. Can be used to slice a ndarray of shape(n, n).

See also

tril_indices : similar function, for lower-triangular. mask_indices : generic function accepting an arbitrary mask function. triu, tril

Notes

New in version 1.4.0.

Examples

Compute two different sets of indices to access 4x4 arrays, one for the upper triangular part starting at the main diagonal, and one starting two diagonals further right:

>>> iu1 = np.triu_indices(4)
>>> iu2 = np.triu_indices(4, 2)

Here is how they can be used with a sample array:

>>> a = np.arange(16).reshape(4, 4)
>>> a
array([[ 0,  1,  2,  3],
       [ 4,  5,  6,  7],
       [ 8,  9, 10, 11],
       [12, 13, 14, 15]])

Both for indexing:

>>> a[iu1]
array([ 0,  1,  2, ..., 10, 11, 15])

And for assigning values:

>>> a[iu1] = -1
>>> a
array([[-1, -1, -1, -1],
       [ 4, -1, -1, -1],
       [ 8,  9, -1, -1],
       [12, 13, 14, -1]])

These cover only a small part of the whole array (two diagonals right of the main one):

>>> a[iu2] = -10
>>> a
array([[ -1,  -1, -10, -10],
       [  4,  -1,  -1, -10],
       [  8,   9,  -1,  -1],
       [ 12,  13,  14,  -1]])
@array_function_dispatch(_trilu_indices_form_dispatcher)
def triu_indices_from(arr, k=0):

Return the indices for the upper-triangle of arr.

See triu_indices for full details.

Parameters

arr : ndarray, shape(N, N)
The indices will be valid for square arrays.
k : int, optional
Diagonal offset (see triu for details).

Returns

triu_indices_from : tuple, shape(2) of ndarray, shape(N)
Indices for the upper-triangle of arr.

See Also

triu_indices, triu

Notes

New in version 1.4.0.
@array_function_dispatch(_vander_dispatcher)
def vander(x, N=None, increasing=False):

Generate a Vandermonde matrix.

The columns of the output matrix are powers of the input vector. The order of the powers is determined by the increasing boolean argument. Specifically, when increasing is False, the i-th output column is the input vector raised element-wise to the power of N - i - 1. Such a matrix with a geometric progression in each row is named for Alexandre- Theophile Vandermonde.

Parameters

x : array_like
1-D input array.
N : int, optional
Number of columns in the output. If N is not specified, a square array is returned (N = len(x)).
increasing : bool, optional

Order of the powers of the columns. If True, the powers increase from left to right, if False (the default) they are reversed.

New in version 1.9.0.

Returns

out : ndarray
Vandermonde matrix. If increasing is False, the first column is x^(N-1), the second x^(N-2) and so forth. If increasing is True, the columns are x^0, x^1, ..., x^(N-1).

See Also

polynomial.polynomial.polyvander

Examples

>>> x = np.array([1, 2, 3, 5])
>>> N = 3
>>> np.vander(x, N)
array([[ 1,  1,  1],
       [ 4,  2,  1],
       [ 9,  3,  1],
       [25,  5,  1]])
>>> np.column_stack([x**(N-1-i) for i in range(N)])
array([[ 1,  1,  1],
       [ 4,  2,  1],
       [ 9,  3,  1],
       [25,  5,  1]])
>>> x = np.array([1, 2, 3, 5])
>>> np.vander(x)
array([[  1,   1,   1,   1],
       [  8,   4,   2,   1],
       [ 27,   9,   3,   1],
       [125,  25,   5,   1]])
>>> np.vander(x, increasing=True)
array([[  1,   1,   1,   1],
       [  1,   2,   4,   8],
       [  1,   3,   9,  27],
       [  1,   5,  25, 125]])

The determinant of a square Vandermonde matrix is the product of the differences between the values of the input vector:

>>> np.linalg.det(np.vander(x))
48.000000000000043 # may vary
>>> (5-3)*(5-2)*(5-1)*(3-2)*(3-1)*(2-1)
48
_eye_with_like =

Undocumented

_tri_with_like =

Undocumented