Entropy
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clear all;
close all;
clc;
x = imread('circuit.tif');
p = imhist(x);
[m,n] = size(p);
E = 0;
for i = 1:m
for j = 1:n
if(p(i,j) > 0)
E = E - (p(i,j) * log2(p(i,j)));
end
end
end
ex = entropy(p);
Why E and ex having different values ? How we can solve it ?
2 个评论
Walter Roberson
2012-6-6
I do not have access at the moment to check: I wonder what the datatype of p is? If it turns out to be one of the integer data types, your expressions probably do not compute what you expect.
Image Analyst
2012-6-6
p is a 1D variable since it's the counts. Also you didn't normalize p by dividing by numel(x).
回答（1 个）
Image Analyst
2012-6-6
Try this:
p(p==0) = [];
E2 = -sum(p .* log2(p))
E3 = entropy(x)
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