## csound-devel

 [Cs-dev] [OT] How to produce IIR filter coefficients from a set of points describing the frequency response From: Andres Cabrera - 2009-05-15 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
 Re: [Cs-dev] [OT] How to produce IIR filter coefficients from a set ofpoints describing the frequency response From: victor - 2009-05-15 18:32:57 scipy has a signal processing module: NAME scipy.signal FILE c:\python25\lib\site-packages\scipy\signal\__init__.py DESCRIPTION Signal Processing Tools ======================= Convolution: convolve -- N-dimensional convolution. correlate -- N-dimensional correlation. fftconvolve -- N-dimensional convolution using the FFT. convolve2d -- 2-dimensional convolution (more options). correlate2d -- 2-dimensional correlation (more options). sepfir2d -- Convolve with a 2-D separable FIR filter. B-splines: bspline -- B-spline basis function of order n. gauss_spline -- Gaussian approximation to the B-spline basis function. cspline1d -- Coefficients for 1-D cubic (3rd order) B-spline. qspline1d -- Coefficients for 1-D quadratic (2nd order) B-spline. cspline2d -- Coefficients for 2-D cubic (3rd order) B-spline. qspline2d -- Coefficients for 2-D quadratic (2nd order) B-spline. spline_filter -- Smoothing spline (cubic) filtering of a rank-2 array. Filtering: order_filter -- N-dimensional order filter. medfilt -- N-dimensional median filter. medfilt2 -- 2-dimensional median filter (faster). wiener -- N-dimensional wiener filter. symiirorder1 -- 2nd-order IIR filter (cascade of first-order systems). symiirorder2 -- 4th-order IIR filter (cascade of second-order systems) . lfilter -- 1-dimensional FIR and IIR digital linear filtering. deconvolve -- 1-d deconvolution using lfilter. hilbert -- Compute the analytic signal of a 1-d 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. Matlab-style 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 -- continuous-time simulation of output to linear system. impulse -- impulse response of linear, time-invariant (LTI) system. step -- step response of continous-time LTI system. LTI Reresentations: tf2zpk -- transfer function to zero-pole-gain. zpk2tf -- zero-pole-gain to transfer function. tf2ss -- transfer function to state-space. ss2tf -- state-pace to transfer function. zpk2ss -- zero-pole-gain to state-space. ss2zpk -- state-space to pole-zero-gain. 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 4-term Blackman-Harris window nuttall -- Nuttall's minimum 4-term Blackman-Harris window flattop -- Flat top window bartlett -- Bartlett window hann -- Hann window barthann -- Bartlett-Hann window hamming -- Hamming window kaiser -- Kaiser window gaussian -- Gaussian window general_gaussian -- Generalized Gaussian window slepian -- Slepian window Wavelets: daub -- return low-pass filter for daubechies wavelets qmf -- return quadrature mirror filter from low-pass cascade -- compute scaling function and wavelet from coefficients Victor ----- Original Message ----- From: "Andres Cabrera" To: "Developer discussions" Sent: Friday, May 15, 2009 12:54 PM Subject: [Cs-dev] [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 royalty-free distribution of the report engine for externally facing server and web deployment. http://p.sf.net/sfu/businessobjects _______________________________________________ Csound-devel mailing list Csound-devel@... https://lists.sourceforge.net/lists/listinfo/csound-devel