For example, in the code below, the variable X appears in the MODEL statement. But, only the product of X with itself (X*X = X**2) appears in the model.

proc transreg data=mydata;
  model identity(y) = ide(x*x);
  output;
run;  

In this situation, the model results will be incorrect. To avoid the problem, build the squared variable in a DATA step.

data newdata;
   set mydata;
   x2=x*x;
   run;

proc transreg data=newdata;
   model identity(y) = ide(x2);
   output;
   run;  

Operating System and Release Information