Thanks for the ideas. I've been playing with sage all afternoon and

it's great. I'd heard about it, but had not dared install it...

But on the topic of iir filter coeficients, I haven't been able to

find how... with scipy.signal, there are two functions for creating

filters: iirfiter and iirdesign, but they are not designed for

arbitrary filter responses, since they model classic bp, hp, lp and br

filters. I've found remez, but it's for fir filters.

Am I missing something?

Cheers,

Andr?s