Mercurial > hg > camir-aes2014
annotate toolboxes/FullBNT-1.0.7/KPMtools/entropy.m @ 0:e9a9cd732c1e tip
first hg version after svn
| author | wolffd |
|---|---|
| date | Tue, 10 Feb 2015 15:05:51 +0000 |
| parents | |
| children |
| rev | line source |
|---|---|
| wolffd@0 | 1 function H = entropy(v, scale) |
| wolffd@0 | 2 % ENTROPY Entropy log base 2 |
| wolffd@0 | 3 % H = entropy(v) |
| wolffd@0 | 4 % If v is a matrix, we compute the entropy of each column |
| wolffd@0 | 5 % |
| wolffd@0 | 6 % % H = entropy(v,1) means we scale the result so that it lies in [0,1] |
| wolffd@0 | 7 |
| wolffd@0 | 8 if nargin < 2, scale = 0; end |
| wolffd@0 | 9 |
| wolffd@0 | 10 v = v + (v==0); |
| wolffd@0 | 11 H = -1 * sum(v .* log2(v), 1); % sum the rows |
| wolffd@0 | 12 |
| wolffd@0 | 13 if scale |
| wolffd@0 | 14 n = size(v, 1); |
| wolffd@0 | 15 unif = normalise(ones(n,1)); |
| wolffd@0 | 16 H = H / entropy(unif); |
| wolffd@0 | 17 end |