Ian, I hit a bug (segfault) in cntr.c that is likely related to your changes. It is ID 2956378 in the tracker. Sample script and data file are there. Will you be able to take a look soon? (Not sure whether the following link will work for you.) https://sourceforge.net/tracker/?func=detail&aid=2956378&group_id=80706&atid=560720 Thanks. Eric