How can you delete a random fraction of entries from a sparse matrix?

a - sparse matrix f - fraction which should be removed

I tried:

nonZeros = nnz(A);
[i,j,s] = find(A);
s = RandStream('mt19937ar','Seed',0);
selection = randperm(s,floor((1-f/100) * nonZeros));
i = i(selection);
j = j(selection);
s = s(selection);
A = sparse(i,j,s);

On line "i = i(selection);" I get the error message: "You cannot index into a RandStream using () indexing."

Answer 1

[Matt J]

You're mixing the usage of s, sometimes using it to refer to the sparse data and sometimes to the RandStream.

[Matt J]

I don't think you need randperm:

 [i,j,s] = find(A);
 numkeep=floor((1-f/100) * length(s));
 selection = randi(length(s),1,numkeep);

i = i(selection);
j = j(selection);
s = s(selection);
A = sparse(i,j,s);