what is the tolerance factor of entropy function used in matlab program to find entropy of image?

e = entropy(I) , which calculates the entropy of the image in matlab. What is the tolerance factor used in this function, and is there any way to varry it?

[Abhishek Kolla]

Entropy is calculated using the formula -sum(p.*log2(p)) where p contains the normalised histogram counts taken from the input image. There is no tolerance factor involved in this calculation