Hi Laura,
This seems very strange to me. Note that it is very strange to
to use polort -1, as that makes regression very difficult. For
that reason, my suspicion is that the errts is or is close to
having a mean of zero, and perhaps that is what is causing
you trouble.
How about just adding 100 to the errts and trying the result?
3dcalc -a errts.SUBJ+tlrc -expr a+100 -prefix errts.100.SUBJ
- rick
