scipy tutorial - Baustatik-Info-Server

See Also:
Returns
L : sparse matrix
Upper triangular portion of A in sparse format.
tril
lower triangle in sparse format
Examples
SciPy Reference Guide, Release 0.8.dev
>>> 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’)
bmat(blocks, format=None, dtype=None)
Build a sparse matrix from sparse sub-blocks
Examples
Parameters
blocks :
grid of sparse matrices with compatible shapes an entry of None implies an all-zero
matrix
format : sparse format of the result (e.g. “csr”)
by default an appropriate sparse matrix format is returned. This choice is subject to
change.
>>> from scipy.sparse import coo_matrix, bmat
>>> A = coo_matrix([[1,2],[3,4]])
>>> B = coo_matrix([[5],[6]])
>>> C = coo_matrix([[7]])
>>> bmat( [[A,B],[None,C]] ).todense()
matrix([[1, 2, 5],
3.14. Sparse matrices (scipy.sparse) 389