PROC REG enables you to change interactively both the model and the data used to compute the model, and to produce and highlight scatter plots. See the section Using PROC REG Interactively for an overview of interactive analysis that uses PROC REG. The following statements can be used interactively (without reinvoking PROC REG): ADD, DELETE, MODEL, MTEST, OUTPUT, PAINT, PLOT, PRINT, REFIT, RESTRICT, REWEIGHT, and TEST. All interactive features are disabled if there is a BY statement.

The ADD, DELETE, and REWEIGHT statements can be used to modify the current MODEL. Every use of an ADD, DELETE, or REWEIGHT statement causes the model label to be modified by attaching an additional number to it. This number is the cumulative total of the number of ADD, DELETE, or REWEIGHT statements following the current MODEL statement.

A more detailed explanation of changing the data used to compute the model is given in the section Reweighting Observations in an Analysis. Extra features for line printer scatter plots are discussed in the section Line Printer Scatter Plot Features.

The following statements illustrate the usefulness of the interactive features. First, the full regression model is fit to the Class data (see the section Getting Started: REG Procedure), and Figure 73.25 is produced.

   ods graphics on;
   
   proc reg data=Class plots(modelLabel only)=ResidualByPredicted;
      model Weight=Age Height;  
   run;