scipy.sparse.tril¶
- scipy.sparse.tril(A, k=0, format=None)[source]¶
Return the lower triangular portion of a matrix in sparse format
- Returns the elements on or below the k-th diagonal of the matrix A.
- k = 0 corresponds to the main diagonal
- k > 0 is above the main diagonal
- k < 0 is below the main diagonal
Parameters: A : dense or sparse matrix
Matrix whose lower trianglar portion is desired.
k : integer
The top-most diagonal of the lower triangle.
format : string
Sparse format of the result, e.g. format=”csr”, etc.
Returns: L : sparse matrix
Lower triangular portion of A in sparse format.
See also
- triu
- upper triangle in sparse format
Examples
>>> from scipy.sparse import csr_matrix >>> A = csr_matrix([[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') <3x5 sparse matrix of type '<type 'numpy.int32'>' with 4 stored elements in Compressed Sparse Column format>