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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 | % SPRAND SPRAND Sparse Uniform Random Matrix
%
% Usage
%
% Creates a sparse matrix with uniformly distributed random entries (on [0,1]). The
% syntax for its use is
%
% y = sprand(x)
%
% where x is a sparse matrix, where y is a sparse matrix that has
% random entries where x is nonzero. The second form specifies the
% size of the matrix and the density
%
% y = sprand(m,n,density)
%
% where m is the number of rows in the output, n is the number of
% columns in the output, and density (which is between 0 and 1) is
% the density of nonzeros in the resulting matrix. Note that for very
% high densities the actual density of the output matrix may differ from
% the density you specify. This difference is a result of the way the
% random entries into the matrix are generated. If you need a very dense
% random matrix, it is better to generate a full matrix and zero out the
% entries you do not need.
% Copyright (c) 2002-2006 Samit Basu
% Licensed under the GPL
function y = sprand(x,n,density)
if (nargin == 1)
[i,j] = find(x);
s = rand(size(i));
y = sparse(i,j,s);
else
m = round(x(1));
n = round(n(1));
density = max(0.0,min(1.0,density(1)));
cnt = round(density*m*n);
if (cnt == 0)
y = sparse(m,n);
return;
end
i = randi(1,m*ones(cnt,1));
j = randi(1,n*ones(cnt,1));
A = [i,j];
A = unique(A,'rows');
i = A(:,1);
j = A(:,2);
s = rand(size(i));
y = sparse(i,j,s,m,n);
end
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