options ls=75;


data one;
   infile "drywt.dat" firstobs=2 dlm='09'x;
   input light temp  i y;
   lt_combo=light+temp/10;  /* light-temp combo */
run;

proc print;run;

proc glm;
   class lt_combo;
   model y=lt_combo;
   estimate "interaction" lt_combo -1 1 1 -1;  /* diff of slopes, 1c */
   contrast "interaction" lt_combo -1 1 1 -1;  /* ss(interaction), 1d*/
   contrast "ss(light)" lt_combo -1 -1 1 1;  /* ss(light), 1d*/
   contrast "ss(temp)" lt_combo -1 1 -1 1;  /* ss(temp), 1d*/

proc glm;
   class light temp;
   *model y=light*temp;  /* for one-way test of mu1=mu2=mu3=mu4 */
   model y=light|temp;  /* for two-factor analysis, 1e */
   output out=plotme p=p;
run;
symbol value=dot i=join;
proc gplot;
   title "interaction plot, problem 1g, hw4";
   plot p*light=temp;
run;