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From: Andres Cabrera <mantaraya36@gm...>  20090515 11:54:15

Hi all, The subject asks the question... What I want to know is if there's an easy way using something like pylab and numpy to produce a set of coefficients for an IIR filter from a given frequency response. I've read on the internet that matlab has the invresz function which does this, but is there an easy way with free software? Cheers Andrés 
From: victor <Victor.L<azzarini@nu...>  20090515 18:32:57

scipy has a signal processing module: NAME scipy.signal FILE c:\python25\lib\sitepackages\scipy\signal\__init__.py DESCRIPTION Signal Processing Tools ======================= Convolution: convolve  Ndimensional convolution. correlate  Ndimensional correlation. fftconvolve  Ndimensional convolution using the FFT. convolve2d  2dimensional convolution (more options). correlate2d  2dimensional correlation (more options). sepfir2d  Convolve with a 2D separable FIR filter. Bsplines: bspline  Bspline basis function of order n. gauss_spline  Gaussian approximation to the Bspline basis function. cspline1d  Coefficients for 1D cubic (3rd order) Bspline. qspline1d  Coefficients for 1D quadratic (2nd order) Bspline. cspline2d  Coefficients for 2D cubic (3rd order) Bspline. qspline2d  Coefficients for 2D quadratic (2nd order) Bspline. spline_filter  Smoothing spline (cubic) filtering of a rank2 array. Filtering: order_filter  Ndimensional order filter. medfilt  Ndimensional median filter. medfilt2  2dimensional median filter (faster). wiener  Ndimensional wiener filter. symiirorder1  2ndorder IIR filter (cascade of firstorder systems). symiirorder2  4thorder IIR filter (cascade of secondorder systems) . lfilter  1dimensional FIR and IIR digital linear filtering. deconvolve  1d deconvolution using lfilter. hilbert  Compute the analytic signal of a 1d signal. get_window  Create FIR window. detrend  Remove linear and/or constant trends from data. resample  Resample using Fourier method. Filter design: remez  Optimal FIR filter design. firwin  Windowed FIR filter design. iirdesign  IIR filter design given bands and gains. iirfilter  IIR filter design given order and critical frequencies. freqs  Analog filter frequency response. freqz  Digital filter frequency response. unique_roots  Unique roots and their multiplicities. residue  Partial fraction expansion of b(s) / a(s). residuez  Partial fraction expansion of b(z) / a(z). invres  Inverse partial fraction expansion. Matlabstyle IIR filter design: butter (buttord)  Butterworth cheby1 (cheb1ord)  Chebyshev Type I cheby2 (cheb2ord)  Chebyshev Type II ellip (ellipord)  Elliptic (Cauer) bessel  Bessel (no order selection available  try butterord) Linear Systems: lti  linear time invariant system object. lsim  continuoustime simulation of output to linear system. impulse  impulse response of linear, timeinvariant (LTI) system. step  step response of continoustime LTI system. LTI Reresentations: tf2zpk  transfer function to zeropolegain. zpk2tf  zeropolegain to transfer function. tf2ss  transfer function to statespace. ss2tf  statepace to transfer function. zpk2ss  zeropolegain to statespace. ss2zpk  statespace to polezerogain. Waveforms: sawtooth  Periodic sawtooth square  Square wave gausspulse  Gaussian modulated sinusoid chirp  Frequency swept cosine signal Window functions: boxcar  Boxcar window triang  Triangular window parzen  Parzen window bohman  Bohman window blackman  Blackman window blackmanharris  Minimum 4term BlackmanHarris window nuttall  Nuttall's minimum 4term BlackmanHarris window flattop  Flat top window bartlett  Bartlett window hann  Hann window barthann  BartlettHann window hamming  Hamming window kaiser  Kaiser window gaussian  Gaussian window general_gaussian  Generalized Gaussian window slepian  Slepian window Wavelets: daub  return lowpass filter for daubechies wavelets qmf  return quadrature mirror filter from lowpass cascade  compute scaling function and wavelet from coefficients Victor  Original Message  From: "Andres Cabrera" <mantaraya36@...> To: "Developer discussions" <csounddevel@...> Sent: Friday, May 15, 2009 12:54 PM Subject: [Csdev] [OT] How to produce IIR filter coefficients from a set ofpoints describing the frequency response Hi all, The subject asks the question... What I want to know is if there's an easy way using something like pylab and numpy to produce a set of coefficients for an IIR filter from a given frequency response. I've read on the internet that matlab has the invresz function which does this, but is there an easy way with free software? Cheers Andrés  Crystal Reports  New Free Runtime and 30 Day Trial Check out the new simplified licensing option that enables unlimited royaltyfree distribution of the report engine for externally facing server and web deployment. http://p.sf.net/sfu/businessobjects _______________________________________________ Csounddevel mailing list Csounddevel@... https://lists.sourceforge.net/lists/listinfo/csounddevel 