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]], 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).nnz 4 >>> 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)>