Rick, Thank you from the ends of the earth and back!!!  That worked like a charm.  I put in print statements like you said so I could see the "magic" happen.  I did not realize that you have to append the last row in the unique_by matrix......I tried taking it off just for fun and it doesn't fill the last row.  So, I'm guessing it is there to make the do loop complete?  Thanks again. Rachel ... View more

Rick, Thanks so much for responding.  Actually I already learned the unique_by statement trick from one of your earlier posts and it is amazing!  Believe it or not, it's the actual indexing statement that is tripping me up.  I already have the ESTS matrix split into submatrices by sample no.  I just can't get the correct observations pulled from it.  I'll show you some of the code: read all var{sample lo hi} into worklim; use thirdsorted; read all var{sample mc3estimates} into workests; unique_rows400=uniqueby(workests,1,1:nrow(workests)); do k=1 to nrow(unique_rows400);  if k=nrow(unique_rows400) then index=unique_rows400 :nrow(workests);  else index=unique_rows400 :unique_rows400[k+1]-1;   submat400=workests[index,];   print submat400; end; I am struggling with something like------ confint=j(nrow(worklim),2,0); confint[i,1:2]=workests[worklim,worklim[i,2]]; Thanks for your help Rick! Rachel ... View more