tril#

scipy.sparse.tril(A,k=0,format=None)[source]#

Return the lower triangular portion of a sparse array or matrix

Returns the elements on or below the k-th diagonal of A.

• k = 0 corresponds to the main diagonal

• k > 0 is above the main diagonal

• k < 0 is below the main diagonal

Parameters:

Adense or sparse array or matrix

Matrix whose lower trianglar portion is desired.

kintegeroptional

The top-most diagonal of the lower triangle.

formatstring

Sparse format of the result, e.g. format=”csr”, etc.

Returns:

Lsparse matrix

Lower triangular portion of A in sparse format.

See also

triu

upper triangle in sparse format

Examples

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>>>fromscipy.sparseimportcsr_array,tril>>>A=csr_array([[1,2,0,0,3],[4,5,0,6,7],[0,0,8,9,0]],...dtype='int32')>>>A.toarray()array([[1, 2, 0, 0, 3],       [4, 5, 0, 6, 7],       [0, 0, 8, 9, 0]], dtype=int32)>>>tril(A).toarray()array([[1, 0, 0, 0, 0],       [4, 5, 0, 0, 0],       [0, 0, 8, 0, 0]], dtype=int32)>>>tril(A).nnz4>>>tril(A,k=1).toarray()array([[1, 2, 0, 0, 0],       [4, 5, 0, 0, 0],       [0, 0, 8, 9, 0]], dtype=int32)>>>tril(A,k=-1).toarray()array([[0, 0, 0, 0, 0],       [4, 0, 0, 0, 0],       [0, 0, 0, 0, 0]], dtype=int32)>>>tril(A,format='csc')<Compressed Sparse Column sparse array of dtype 'int32'    with 4 stored elements and shape (3, 5)>

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