Hi, I've noticed that in contrast to 'ols' the 'var' command is not clever enough to see when a regressor is linearly redundant. Example: <hansl> nulldata 10 setobs 1 1 --time-series series x = normal() series y = 0 var 1 x y # error matrix not pos.def. </hansl> The error message appears to refer to X'X and is coming from gretl's internals. Maybe some pre-checks would be good, similar to what 'ols' does. thanks, sven