options ls=80 ps=64;
data a;
   infile 'grain.dat' firstobs=2;
   input farm lact past $ trt $ yield;
proc glm;
   class farm lact past trt;
   model yield = farm lact | past | trt;
proc sort; by lact;
proc glm; by lact;
   class farm past trt;
   model yield = farm past | trt;
   lsmeans past*trt / stderr out=lsm;
   output out=diag r=ryield p=pyield;
proc plot data=lsm; by lact;
   plot lsmean*past=trt;
proc plot data=diag; by lact;
   plot ryield*pyield=trt;