options nodate nonumber ps=54 ls=80;

data arg_wheat;
infile "argentine_wheat.dat";
input year 1-8 wheatyld 9-16 rain 17-24 temp 25-32;
raintemp=rain*temp;
run;

ods PDF file="argwheat_sas1.pdf";
ods graphics on;

proc reg plots=diagnostics plots(label)=(residuals);
var year;
model wheatyld = rain temp raintemp / dw;
output out=arg_wheat_r r=e;
run;

data arg_wheat_r; set arg_wheat_r;   e2=e**2;

proc reg;
model e2 = rain temp raintemp;
run;

ods graphics off;


ods PDF close;

quit;

proc model data=arg_wheat;
parms b0 b1 b2 b3;
wheatyld = b0 + b1*rain + b2*temp + b3*raintemp;
fit wheatyld / breusch = (1 rain temp raintemp);   /* This is based on studentized residuals  */
run;

quit;