Using the Group By option, you can select a classification (grouping) variable. When a grouping variable is in effect, the Bivariate platform computes a separate analysis for each level of the grouping variable. Regression curves or ellipses then appear on the scatterplot. The fit for each level of the grouping variable is identified beneath the scatterplot, with individual popup menus to save or remove fitting information.
The Group By option is checked in the Fitting menu when a grouping variable is in effect. You can change the grouping variable by first selecting the Group By option to remove (uncheck) the existing variable. Then, select the Group By option again and respond to its window as before.