--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/matrixcomp/sparsify.m	Wed May 06 14:56:53 2015 +0200
@@ -0,0 +1,20 @@
+function A = sparsify(A, p)
+%SPARSIFY  Randomly set matrix elements to zero.
+%          S = SPARSIFY(A, P) is A with elements randomly set to zero
+%          (S = S' if A is square and A = A', i.e. symmetry is preserved).
+%          Each element has probability P of being zeroed.
+%          Thus on average 100*P percent of the elements of A will be zeroed.
+%          Default: P = 0.25.
+
+if nargin < 2, p = 0.25; end
+if p<0 | p>1, error('Second parameter must be between 0 and 1 inclusive.'), end
+
+[m,n] = size(A);
+
+if ~isequal(A,A')
+   A = A .* (rand(m,n) > p);        % Unsymmetric case
+else
+   A = triu(A,1) .* (rand(m,n) > p);  % Preserve symmetry
+   A = A + A';
+   A = A + diag( diag(A) .* (rand(size(n,1)) > p) );
+end