How do I switch a column of data from "y" to "x"?

I am trying to do a cobweb graph for a function as a math project in Pages. I need to create two separate cobwebs. In the first one the two columns of data needed for the cobweb are labeled as "x" and "y" and the proper lines appear. However, on my second graph I can't get the first column to appear as "x" instead of "y", so instead of the two columns being x and y coordinates, I end up with two lines on the graph instead of just the one that I need. A solution for this is needed as soon as possible. Try and keep the help simple too--I'm not an expert with pages AT all.

Maddy