title: How to solve the .mat file sorting?
body: <p>I have three .mat files, A.mat, B.mat and C.mat. And the content of the .mat files look like this:
  ![enter image description here][1]</p>
  
  <p>It is in r2 = [rs2,cs2,sortedValues2] format. How can I sort rs2(e.g, 3468, 3909...) of the three 
  .mat files together in increasing order, and count the number of appearance of each element of rs2?
  Anyone can give me any suggestion?</p>