title: Adding a curve to Matlab Figure
body: <p>I have written a program that takes a lot of data and produces graphs.It would be really convenient and save me a lot of time if I could take curves on an existing figure and add their values together to make a single curve. For a simple example lets say I have the following code,</p>
  
  <pre><code>x = [0 1 2 3 4 5];
  y = [0 1 2 3 4 5];
  z = [4 6 2 8 7 9];
  
  figure
  plot(x,y,x,z)   
  </code></pre>
  
  <p>This code will produce a figure with two curves. Without modifying the code or re-running the program, and only working with the figure options I would like to add the curve y + z to the plot. Is this possible? Thanks.</p>
  
  <p>The reason I don't want to add the functionality is the plot code is buried within 8 loops 
  that calls data from a 4D cell array of file name strings.</p>