The answer is NaN

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Huy
Huy 2013-12-25
评论： Huy 2013-12-26
I don't know why the answer of this code is NaN. Help me please. thanks so much
for a = 01:20
filename = [num2str(a,'%02d') '_training' '.tif'];
img = imread(filename);
img1=imrotate(img,90,'bilinear');
C=rgb2gray(img1);
%co-occurrence matrix
glcm=graycomatrix(C,'GrayLimits',[0 255],'NumLevels',256,'Offset',[-1 -1]);
p=glcm/sum(glcm(:));
entropy=0;
for i=1:256
for j =1:256
entropy=entropy-p(i,j)*log2(p(i,j));
end
end
kq(a,:)=[entropy];
end

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采纳的回答

Matt J
Matt J 2013-12-25
What prevents p(i,j) from being 0 in
entropy=entropy-p(i,j)*log2(p(i,j));
Note
>> 0*log(0)
ans =
NaN
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显示 1更早的评论
Matt J
Matt J 2013-12-25
编辑：Matt J 2013-12-25
if p(i,j)==0
blablabla
end
or, discarding the for-loops,
entropy=p.*log(p);
entropy(isnan(entropy)) = blablabla
Huy
Huy 2013-12-25
thanks so much

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更多回答（1 个）

Image Analyst
Image Analyst 2013-12-25
Often a small number is added to values before taking log
smallNumber = 1; % % Whatever...
p(p==0) = smallNumber;
Now do your log.

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