spSubmat¶
Purpose¶
Returns a sparse submatrix of a sparse matrix.
Format¶
-
s =
spSubmat(x, rinds, cinds)¶ - Parameters
x (MxN sparse matrix) – data
rinds (Kx1 vector) – row indices.
cinds (Lx1 vector) – column indices.
- Returns
s (KxL sparse matrix) – the intersection of rinds and cinds.
Examples¶
sparse matrix y;
sparse matrix z;
x = { 0 0 0 10,
0 2 0 0,
0 0 0 0,
5 0 0 0,
0 0 0 3 };
y = denseToSp(x, 0);
// Extract all columns; rows 1, 3 and 4
z = spSubmat(y, 1|3|4, 0);
// Extract all values from 'z' into a dense matrix 'd'
d = spToDense(z);
Now d is equal to:
0.00 0.00 0.00 10.00
0.00 0.00 0.00 0.00
5.00 0.00 0.00 0.00
Remarks¶
If rinds or cinds are scalar zeros, all rows or columns will be returned.
Since sparse matrices are strongly typed in GAUSS, y must be defined as
a sparse matrix before the call to spSubmat().
See also
Functions spDenseSubmat()