[PD] algorithms for drawing filter response curves

[Hans-Christoph Steiner]

On Feb 7, 2011, at 6:12 AM, volker böhm wrote:

>
> On 07.02.2011, at 00:12, Hans-Christoph Steiner wrote:
>
>>
>> I've started to write a GUI for generating biquad coefficients  
>> (something like Max/MSP's [filtergraph~]).  I've gotten the GUI  
>> interaction working well, now I'm looking for the algorithms for  
>> generating a plot of the frequency response of a given set of  
>> biquad coefficents?  It'll end up being Tcl, but I can easily read  
>> C, Csound, Java, Perl, Python, etc.
>>
>> .hc
>
> i've been using the attached js file to query amplitude and phase  
> response of biquad coeffs,
> where the coeffs are expected to be of the form: y[n] = a0 * x[n] +  
> a1 * x[n-1] + a2 * x[n-2] - b1 * y[n-1] - b2 * y[n-2] (like in  
> maxmsp).
> so, you'd have to rearrage the coeffs and turn the sign of the fb  
> coeffs to make it work with the pd biquad~.
>
> vb
>
> <queryBiquad.js>

Thanks, that helped.  Here's what I have so far: I got the mouse  
interaction almost completed, now I'm just starting the plotting part,  
which has a ways to go.

.hc
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