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()

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