______________________________________________________________________________
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
bool lowpass
Generate a low-pass filter (1) or a high-pass filter (0)
integer lowpass
The order of the filter to be generated
double samplefreq
Sampling frequency of the data series
double cutofffreq
Cut-off frequency for the filter
::math::filters::filter coeffs data
Filter the entire data series
based on the filter coefficients.
list coeffs
List of coefficients as generated by filterButterworth (or in fact any similar list of coefficients)
list data
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 coeffs
List of coefficients as generated by filterButterworth (or in fact any similar list of coefficients)
list yinit
(Optional) initial data for the filter result.
$filterObj filter x
Filter a single value and
return the result.
double x
The value to be filtered
$filterObj reset
Reset the filter object (start anew)
digital, filtering
Mathematics
Copyright (c) 2020 by Arjen Markus