Thank you. Fixing the 'a' allowed it to run through the loop. However, now I am having trouble graphing the results. I have stata 10 and tried to set it back to stata 7 as per one of the earlier post but it did not work. My "y axis" lines up at -1 to 1, the same as my x-axis. This is the code I used for the graph as p:

 

sort xaxis