/*
 * This macro can be used to generate two-factor interaction plot.
 *
 * dataname: name of the dataset.
 * response: response in the regression model.
 * var1, var2: name of two factors.
 *
 * Example:
 *------------------------------------------------

  data filter;
     do D = -1 to 1 by 2; do C = -1 to 1 by 2; 
     do B = -1 to 1 by 2; do A = -1 to 1 by 2;
        input y @@;  output;
     end; end; end; end;
  datalines;
  45 71 48 65 68 60 80 65 43 100 45 104 75 86 70 96
  ;

  symbol1 v = circle c = red  i = join;
  symbol2 v = square c = blue i = join;
  %interplot(filter, y, A, C);

 *------------------------------------------------
 *
 * Peng Zeng, Auburn University
 * 07-03-2007
 *
 */

%macro interplot(dataname, response, var1, var2);
   proc sort data = &dataname;
      by &var1 &var2;
   run;

   proc means noprint data = &dataname;
      var &response; by &var1 &var2;
      output out = ymeanac mean = mn;
   run;

   proc gplot data = ymeanac;
      plot mn * &var1 = &var2;
      plot mn * &var2 = &var1;
   run;
%mend interplot;