title: Reading values in MATLAB and assigning coordinates to the entries
body: <p>I'm a bit new to MATLAB. </p>
  
  <p>Basically, I have a 20x20 values , complete with various random entries ranging from 0 to 3. I need to write a program that reads this 20x20 square, and assigns x-y coordinates to the entries, so that when I ask for an input of a particular x-y coordinate which has, say an entry of 3, then it will result in an error.
  I'm a bit overwhelmed - but I understand the general concept of what I'm supposed to be finding. I'm wondering if I should use a plot instead to help me. </p>