scipy.sparse.triu

scipy.sparse.triu(A, k=0, format=None)

Return the upper triangular portion of a matrix in sparse format

Returns the elements on or above 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 upper trianglar portion is desired.

k : integer

The bottom-most diagonal of the upper triangle.

format : string

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

Returns:

L : sparse matrix

Upper triangular portion of A in sparse format.

See also

tril

lower 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.todense()
matrix([[1, 2, 0, 0, 3],
        [4, 5, 0, 6, 7],
        [0, 0, 8, 9, 0]])
>>> triu(A).todense()
matrix([[1, 2, 0, 0, 3],
        [0, 5, 0, 6, 7],
        [0, 0, 8, 9, 0]])
>>> triu(A).nnz
8
>>> triu(A, k=1).todense()
matrix([[0, 2, 0, 0, 3],
        [0, 0, 0, 6, 7],
        [0, 0, 0, 9, 0]])
>>> triu(A, k=-1).todense()
matrix([[1, 2, 0, 0, 3],
        [4, 5, 0, 6, 7],
        [0, 0, 8, 9, 0]])
>>> triu(A, format='csc')
<3x5 sparse matrix of type '<type 'numpy.int32'>'
        with 8 stored elements in Compressed Sparse Column format>