How to plot a 2D histogram of pixel pairs ?

I have a 'M by 2' matrix consisting of pixel pairs in an image. I want to find which pixel pairs occur more frequently. For this I need to plot a 2D histogram. Any suggestions ?

Answer 1

[Azzi Abdelmalek]

This looks like the previous question

If you can find the frequency of each pair, then you can find the most frequent one.

A=[1 2;3 4;1 2;5 6;1 2;5 6]
[ii,jj,kk]=unique(A,'rows')
f=histc(kk,1:numel(jj))
[a,idx]=max(f)
out=[ii(idx,:) a]

Answer 2

[Image Analyst]

There is a special function made to exactly that. It's called graycomatrix() and is in the Image Processing Toolbox. It calculates what is called the Gray Level Cooccurrence Matrix. The GLCM is what you called the 2D histogram. My demo script is attached below in blue text. I show the GLCM as a 2D image, like a heat map.