I'm having difficulty selecting x, y, and z axis variables for the Contour Profiler.

My dataset contains 11 columns, and while I can select the response (z) variables by selecting and dragging columns into the "Y, Prediction Formula" area, I seem to have no choice which of the remaining columns are plotted on the x and y axes.

There must be a simple way to select the x and y axes, I just can't figure it out at the moment.

Any help is much appreciated. Thanks!

Robert