title: two dimensional histogram of an image in matlab
body: <p>I have an image. i am calculating I,u,v  components for it.</p>
  
  <p><code>I = (R+G+B)/3</code></p>
  
  <p><code>u = R-G</code></p>
  
  <p><code>v=  G-B;</code></p>
  
  <p>Now , I want to find two-dimensional histograms
  over the chromatic information (u; v).</p>
  
  <p>Thanks in advance. </p>