##### 22.6.2.18 spalloc

— Function File: s = spalloc (r, c, nz)

> Returns an empty sparse matrix of size r-by-c. As Octave resizes sparse matrices at the first opportunity, so that no additional space is needed, the argument nz is ignored. This function is provided only for compatiability reasons.

> It should be noted that this means that code like

>               k = 5;
>               nz = r * k;
>               s = spalloc (r, c, nz)
>               for j = 1:c
>                 idx = randperm (r);
>                 s (:, j) = [zeros(r - k, 1); rand(k, 1)] (idx);
>               endfor

> will reallocate memory at each step. It is therefore vitally important that code like this is vectorized as much as possible.

> See also: sparse, nzmax.