I was wondering if anyone has figured out a way to easily plot categories within a scatter plot. Technically the way to do it is to manually create a separate series for each category and plot your X,Y data. However, adding series can be time consuming and cumbersome. I've used a software package called Minitab in the past and they have a fantastic utility. The inputs are enter x data, y data, and the category you want to change the symbols by. For instance if I wanted to create a plot of efficiency vs age by product line I would enter:

X: age
Y: efficiency
Category: product line

In seconds I could create an informative plot of all 15 product lines. In excel, adding 20 series could be quite painful.