MATLAB: Why am i getting NaN from the function

Question

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!

Answer 1

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));