* GFClocks Example
  Set up a regression model with interaction to
  predict the price of a grandfather clock
  from the age of the clock and number of bids;

options linesize=70 nodate pageno=1;
data gfclocks;
   infile "c:/datasets/gfclocks.txt" firstobs=2;
   input age nbids price;
   interact = age * nbids;
   label age="Age of Clock"
        nbids="Number of Bids at Auction"
        price="Auction Price of Clock"
        interact="Interaction between age and nbids";

* Obtain parameter estimates and residual plots
  for interaction model;
proc reg;
   title "GFClocks Example";
   model price = age nbids interact;
   plot r.*p. r.*nqq.;

* Use proc glm to obtain parameter estimates and plots;
proc glm;
   model price=age nbids age*nbids;
   output out=out r=resid p=predict;

proc gplot;
   plot resid * predict;

run;
quit;