Filter delay

[Pierre]

Hi.

First of all thanks for this great contribution. Sigpack is very nice.

One question : is plan to handle initial and final conditions of the filter delays (zi and zf) (like matlab does)?
[y, zf] = filter(b,a,x,zi)

This would be very nice to implement properly zero phase filter.

Could you recommand a library that computes butterworth coefficient ?

Thanks again for your help
Pierre

[Claes Rolen]

Actually this is already partly handled in SigPack since the filter itself is a class and the internal state will be encapsulated within the class between calls of filter() or the filter operator. That means that consecutive calls to the filter function

  iir_filt.set_coeffs(b, a);
  Y1 = iir_filt.filter(X1);
  Y2 = iir_filt.filter(X2);

will behave like the Matlab version

[Y1, ZF1] = filter(b,a,X1);
[Y2, ZF2] = filter(b,a,X2,ZF1);

However, there is no direct function to set and get the internal state. As a temporary workaround you could change the b_buf class member to be public or add a set and a get function. Maybe I can add this feature in the next release. Regarding the butterworth and other IIR/FIR filter design tools I have planned to implement them but do not know when I will have time to do it ...
BR Claes