Mercurial > matrix-functions
comparison toolbox/sparsify.m @ 2:c124219d7bfa draft
Re-add the 1995 toolbox after noticing the statement in the ~higham/mctoolbox/ webpage.
| author | Antonio Pino Robles <data.script93@gmail.com> |
|---|---|
| date | Thu, 07 May 2015 18:36:24 +0200 |
| parents | 8f23314345f4 |
| children |
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| 1:e471a92d17be | 2:c124219d7bfa |
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| 1 function A = sparsify(A, p) | |
| 2 %SPARSIFY Randomly sets matrix elements to zero. | |
| 3 % S = SPARSIFY(A, P) is A with elements randomly set to zero | |
| 4 % (S = S' if A is square and A = A', i.e. symmetry is preserved). | |
| 5 % Each element has probability P of being zeroed. | |
| 6 % Thus on average 100*P percent of the elements of A will be zeroed. | |
| 7 % Default: P = 0.25. | |
| 8 | |
| 9 if nargin < 2, p = 0.25; end | |
| 10 if p<0 | p>1, error('Second parameter must be between 0 and 1 inclusive.'), end | |
| 11 | |
| 12 % Is A square and symmetric? | |
| 13 symm = 0; | |
| 14 if min(size(A)) == max(size(A)) | |
| 15 if norm(A-A',1) == 0, symm = 1; end | |
| 16 end | |
| 17 | |
| 18 if ~symm | |
| 19 A = A .* (rand(size(A)) > p); % Unsymmetric case | |
| 20 else | |
| 21 A = triu(A,1) .* (rand(size(A)) > p); % Preserve symmetry | |
| 22 A = A + A'; | |
| 23 A = A + diag( diag(A) .* (rand(size(diag(A))) > p) ); | |
| 24 end |