scipy tutorial - Baustatik-Info-Server

SciPy Reference Guide, Release 0.8.dev
See Also:
Returns
L : sparse matrix
Lower triangular portion of A in sparse format.
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.todense()
matrix([[1, 2, 0, 0, 3],
[4, 5, 0, 6, 7],
[0, 0, 8, 9, 0]])
>>> tril(A).todense()
matrix([[1, 0, 0, 0, 0],
[4, 5, 0, 0, 0],
[0, 0, 8, 0, 0]])
>>> tril(A).nnz
4
>>> tril(A, k=1).todense()
matrix([[1, 2, 0, 0, 0],
[4, 5, 0, 0, 0],
[0, 0, 8, 9, 0]])
>>> tril(A, k=-1).todense()
matrix([[0, 0, 0, 0, 0],
[4, 0, 0, 0, 0],
[0, 0, 0, 0, 0]])
>>> tril(A, format=’csc’)
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.
388 Chapter 3. Reference