title: MATLAB function to swap two letters
body: <p>Let's say I write a script that first asks the user to
  enter a string. </p>
  
  <p>Then, the script asks the user to enter two letter positions and eventually prints the new string with the two chosen letters swapped. </p>
  
  <p>Here is an example of the execution:</p>
  
  <p><strong>Please enter a string: I am studying in ASU</strong></p>
  
  <p><strong>Please enter the index of the first letter: 3</strong></p>
  
  <p><strong>Please enter the index of the second letter: 8</strong></p>
  
  <p><strong>I um stadying in ASU</strong></p>
  
  <p>What function do I use to swap the letters? </p>