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butter

Generate a Butterworth filter.

Description

Generate Butterworth filter polynomial coefficients.

Usage

## Default S3 method:
butter(n, W, type = c("low", "high", "stop", "pass"),
plane = c("z", "s"), ...)

## S3 method for class 'FilterOfOrder'
butter(n, ...)

Arguments

n

filter order or generic filter model
W

critical frequencies of the filter. W must be a scalar for low-pass and high-pass filters, and W must be a two-element vector c(low, high) specifying the lower and upper bands. For digital filters, W must be between 0 and 1 where 1 is the Nyquist frequency.
type

Filter type, one of "low" for a low-pass filter, "high" for a high-pass filter, "stop" for a stop-band (band-reject) filter, or "pass" for a pass-band filter.

plane

"z" for a digital filter or "s" for an analog filter.

...

additional arguments passed to butter, overriding those given by n of class FilterOfOrder.

Details

Because butter is generic, it can be extended to accept other inputs, using "buttord" to generate filter criteria for example.

Value

An Arma object with list elements:

b

moving average (MA) polynomial coefficients

a

autoregressive (AR) polynomial coefficients

Author(s)

Original Octave version by Paul Kienzle pkienzle@user.sf.net. Modified by Doug Stewart. Conversion to R by Tom Short.

References

Proakis & Manolakis (1992). Digital Signal Processing. New York: Macmillan Publishing Company.

Octave Forge http://octave.sf.net

See Also

Examples

bf <- butter(4, 0.1)
  freqz(bf)
  zplane(bf)
signal

Signal Processing

v0.7-6
GPL-2
Authors
Uwe Ligges [aut, cre] (new maintainer), Tom Short [aut] (port to R), Paul Kienzle [aut] (majority of the original sources), Sarah Schnackenberg [ctb] (various test cases and bug fixes), David Billinghurst [ctb], Hans-Werner Borchers [ctb], Andre Carezia [ctb], Pascal Dupuis [ctb], John W. Eaton [ctb], E. Farhi [ctb], Kai Habel [ctb], Kurt Hornik [ctb], Sebastian Krey [ctb], Bill Lash [ctb], Friedrich Leisch [ctb], Olaf Mersmann [ctb], Paulo Neis [ctb], Jaakko Ruohio [ctb], Julius O. Smith III [ctb], Doug Stewart [ctb], Andreas Weingessel [ctb]
Initial release
2015-07-29

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