This is a propos the thread started by Javier Sansa at http://lists.wfu.edu/pipermail/gretl-users/2016-March/011708.html I have now re-enabled the "rename" command in loops, thus reverting to the situation as of the 2015a release. This is because I've come up with a method that I'm comfortable with, for ensuring that renaming doesn't cause problems. Instead of trying to figure out what cases of "rename" are problematic and what cases OK, this is the approach: (1) You can use "rename" at will, but (2) we check if a loop (or in the general case, a stack of nested loops) involves any cases of "rename" (quite easy), and if so (3) we temporarily disable the particular loop-optimization which is vulnerable to renaming. Here's a little illustration: <hansl> open data4-1 loop i=1..6 -q x = max(price) / max(sqft) printf "x = %g\n", x rename sqft tmp rename price sqft rename tmp price endloop Since this loop swaps the numerical content associated with the identifiers "price" and "sqft", the scalar x should take on different values on odd- and even-numbered iterations. And it does. The price is that we have to look up the ID numbers (positions within the dataset) of "price" and "sqft" on each iteration. If we were sure there was no renaming going on, we would look up the ID numbers once and reuse that information on subsequent iterations. Note that (since we're not trying to be "too clever" here) _any_ instance of renaming in a loop means that _all_ series ID numbers will be looked up anew on each iteration of the loop, for safety's sake. But that's not really a big deal unless you're running a potentially quite time-consuming script. Allin