check_symmetric

sklearn.utils.validation.check_symmetric(array, *, tol=1e-10, raise_warning=True, raise_exception=False)

Make sure that array is 2D, square and symmetric.

If the array is not symmetric, then a symmetrized version is returned. Optionally, a warning or exception is raised if the matrix is not symmetric.

Parameters:

array{ndarray, sparse matrix}

Input object to check / convert. Must be two-dimensional and square, otherwise a ValueError will be raised.

tolfloat, default=1e-10

Absolute tolerance for equivalence of arrays. Default = 1E-10.

raise_warningbool, default=True

If True then raise a warning if conversion is required.

raise_exceptionbool, default=False

If True then raise an exception if array is not symmetric.

Returns:

array_sym{ndarray, sparse matrix}

Symmetrized version of the input array, i.e. the average of array and array.transpose(). If sparse, then duplicate entries are first summed and zeros are eliminated.

Examples

>>> import numpy as np
>>> from sklearn.utils.validation import check_symmetric
>>> symmetric_array = np.array([[0, 1, 2], [1, 0, 1], [2, 1, 0]])
>>> check_symmetric(symmetric_array)
array([[0, 1, 2],
       [1, 0, 1],
       [2, 1, 0]])
>>> from scipy.sparse import csr_matrix
>>> sparse_symmetric_array = csr_matrix(symmetric_array)
>>> check_symmetric(sparse_symmetric_array)
<3x3 sparse matrix of type '<class 'numpy.int64'>'
    with 6 stored elements in Compressed Sparse Row format>