1math::filters(n)               Tcl Math Library               math::filters(n)
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NAME

8       math::filters - Digital filters
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SYNOPSIS

11       package require Tcl  8.6
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13       package require TclOO
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15       package require math::filters  ?0.1?
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17       ::math::filters::filterButterworth lowpass order samplefreq cutofffreq
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19       ::math::filters::filter coeffs data
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21       ::math::filters::filterObj new coeffs yinit
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23       $filterObj filter x
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25       $filterObj reset
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DESCRIPTION

30       The  math::filters  package implements digital filters, notably Butter‐
31       worth low-pass and high-pass filters. The procedures allow to filter an
32       entire data series as well as filter data one by one.
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PROCEDURES

35       The package defines the following public procedures:
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37       ::math::filters::filterButterworth lowpass order samplefreq cutofffreq
38              Determine the coefficients for a Butterworth filter of given or‐
39              der. The coefficients are returned as a list  of  the  x-coeffi‐
40              cients,  the  y-coefficients and the scale. The formula is (n is
41              the filter order):
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44                                 n             n
45                  scale * y_k = sum x_(k-i) + sum y_(k-i)
46                                i=0           i=1
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49              bool lowpass
50                     Generate a low-pass filter (1) or a high-pass filter (0)
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52              integer lowpass
53                     The order of the filter to be generated
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55              double samplefreq
56                     Sampling frequency of the data series
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58              double cutofffreq
59                     Cut-off frequency for the filter
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61       ::math::filters::filter coeffs data
62              Filter the entire data series based on the filter coefficients.
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64              list coeffs
65                     List of coefficients as  generated  by  filterButterworth
66                     (or in fact any similar list of coefficients)
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68              list data
69                     Data to be filtered
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71       ::math::filters::filterObj new coeffs yinit
72              Create  a  filter  object. The initial x data are taken as zero.
73              The initial y data can be prescribed. If  they  are  not  given,
74              they are taken as zero as well.
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76              list coeffs
77                     List  of  coefficients  as generated by filterButterworth
78                     (or in fact any similar list of coefficients)
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80              list yinit
81                     (Optional) initial data for the filter result.
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83       $filterObj filter x
84              Filter a single value and return the result.
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86              double x
87                     The value to be filtered
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89       $filterObj reset
90              Reset the filter object (start anew)
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KEYWORDS

93       digital, filtering
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CATEGORY

96       Mathematics
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99       Copyright (c) 2020 by Arjen Markus
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104tcllib                                0.1                     math::filters(n)
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