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math::filters(3tcl) Tcl Math Library math::filters(3tcl) 







math::filters - Digital filters








package require Tcl 8.6


package require TclOO 


package require math::filters ?0.1?


::math::filters::filterButterworth lowpass
    order samplefreq cutofffreq


::math::filters::filter coeffs data


::math::filters::filterObj new coeffs
  yinit


$filterObj filter x


$filterObj reset












The math::filters package implements digital filters,
    notably Butterworth low-pass and high-pass filters. The procedures allow to
    filter an entire data series as well as filter data one by one.








The package defines the following public procedures:



  
::math::filters::filterButterworth lowpass order
    samplefreq cutofffreq

  
Determine the coefficients for a Butterworth filter of given order. The
      coefficients are returned as a list of the x-coefficients, the
      y-coefficients and the scale. The formula is (n is the filter order):








                   n             n


    scale * y_k = sum x_(k-i) + sum y_(k-i)


                  i=0           i=1








  

  
Generate a low-pass filter (1) or a high-pass filter (0)

  

  
The order of the filter to be generated

  

  
Sampling frequency of the data series

  

  
Cut-off frequency for the filter







  
::math::filters::filter coeffs data

  
Filter the entire data series based on the filter coefficients.







  

  
List of coefficients as generated by filterButterworth (or in fact
      any similar list of coefficients)

  

  
Data to be filtered







  
::math::filters::filterObj new coeffs yinit

  
Create a filter object. The initial x data are taken as zero. The initial
      y data can be prescribed. If they are not given, they are taken as zero as
      well.







  

  
List of coefficients as generated by filterButterworth (or in fact
      any similar list of coefficients)

  

  
(Optional) initial data for the filter result.







  
$filterObj filter x

  
Filter a single value and return the result.







  

  
The value to be filtered







  
$filterObj reset

  
Reset the filter object (start anew)










digital, filtering








Mathematics








Copyright (c) 2020 by Arjen Markus








  

    0.1
    tcllib