scipy.sparse.
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
>>> from scipy.sparse import csr_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]]) >>> tril(A).toarray() array([[1, 0, 0, 0, 0], [4, 5, 0, 0, 0], [0, 0, 8, 0, 0]]) >>> tril(A).nnz 4 >>> tril(A, k=1).toarray() array([[1, 2, 0, 0, 0], [4, 5, 0, 0, 0], [0, 0, 8, 9, 0]]) >>> tril(A, k=-1).toarray() array([[0, 0, 0, 0, 0], [4, 0, 0, 0, 0], [0, 0, 0, 0, 0]]) >>> tril(A, format='csc') <Compressed Sparse Column sparse array of dtype 'int32' with 4 stored elements and shape (3, 5)>