[PD] algorithms for drawing filter response curves

[Spencer Russell]

On Sun, Feb 6, 2011 at 11:15 PM, Mathieu Bouchard <matju at artengine.ca> wrote:
> On Sun, 6 Feb 2011, Spencer Russell wrote:
>
>> [1] gives the magnitude frequency response given the biquad
>> coefficents, and it linked to from several places around the net. Is
>> this the sort of thing you're looking for?
>> [1] http://bit.ly/eFck4j
>
> This link got me directly to :
>
>  USB complete: everything you need to develop custom USB peripherals
>  Par Jan Axelson
>  Chapitre 12
>  Page 364
>
> and nothing else. (??)
>

Whoops, I meant to send this: http://bit.ly/gUCBu4. Sorry.

Here he's basically just taken the transfer function of a biquad and
made the z = exp(j*w/Fs) as Mike suggested, followed by taking the
magnitude and log-scaling for dB, but he's done the algebraic legwork.
Just note that w (lower-case omega) is 2*pi*f and you should be good
to go. He's also done some trig-substitution for more numerical
precision.

-s