title: Efficient way of finding average difference between elements in array
body: <p>Hope title isn't confusing.  It's simple to show by example.  I have a row vector like so: <code>[1 5 6]</code>.  I want to find the average difference between each element.  The differences in this example are 4 and 1 so the average is 2.5.  This is a small example.  My row vectors might be very large.  I'm new to MatLab so is there some efficient way of using MATLAB's efficient matrix/array manipulation to do this nicely?</p>
  
  <p>There is a similar question on SOF already but this question is specifically for MATLAB!</p>
  
  <p>Thanks :) </p>
  
  <p>EDIT: As queried by @gnovice, I wanted the absolute difference.</p>