On Wed, Mar 14, 2012 at 08:58:20AM +0100, Rafael Laboissiere wrote: > Since I get the same values for a and b as yours, the only conceivable > source of divergence is the filter function. What does "which filter" > yield for you? I've put a .mat file with the variables after running your commands at http://people.debian.org/~tweber/logs/pei_tseng_notch.mat.lzma Can you compare the variables with your workspace? Thanks Thomas