![Add a diagonal line to a scatter plot](https://blogs.sas.com/content/iml/files/2011/06/diagline-640x336.png)
In my statistical analysis of coupons article, I presented a scatter plot that includes the identity line, y=x. This post describes how to write a general program that uses the SGPLOT procedure in SAS 9.2. By a "general program," I mean that the program produces the result based on the