why am i getting NaN from my function
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tomer orenshtein
el 26 de En. de 2020
Comentada: tomer orenshtein
el 26 de En. de 2020
i was asked to write a function that gets b&w image and returns its entropy. im not allowed to use im_hist or entrtopy (obviously).
this is the function i wrote:
function [Entropy] = EntropyCalc(image)
image_hist = histogram(image);
values = image_hist.Values;
[size_x, size_y] = size(image);
total = size_x * size_y;
p = values./total;
Entropy = - sum(p.*log2(p));
end
but i keep getting NaN.
any ideas??
thanks!
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Thiago Henrique Gomes Lobato
el 26 de En. de 2020
As David said your log2(p) is not safe, you can solve this problem by using this line of code:
Entropy = - sum(p.*log2(p+eps));
3 comentarios
Thiago Henrique Gomes Lobato
el 26 de En. de 2020
Editada: Thiago Henrique Gomes Lobato
el 26 de En. de 2020
The difference is in the histogram function, you need to explicitely define the number of bins to 256 (make sure image is uint8) so it has the same result.
image_hist = histogram(image,256);
Or faster:
values = imhist(image(:));
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