butter {signal} | R Documentation |
Generate Butterworth filter polynomial coefficients.
## Default S3 method: butter(n, W, type = c("low", "high", "stop", "pass"), plane = c("z", "s"), ...) ## S3 method for class 'FilterOfOrder': butter(n, ...)
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 . |
Because butter
is generic, it can be extended to accept other
inputs, using "buttord"
to generate filter criteria for example.
An Arma
object with list elements:
b |
moving average (MA) polynomial coefficients |
a |
autoregressive (AR) polynomial coefficients |
Original Octave version by Paul Kienzle pkienzle@user.sf.net. Modified by Doug Stewart. Conversion to R by Tom Short.
Proakis & Manolakis (1992). Digital Signal Processing. New York: Macmillan Publishing Company.
http://en.wikipedia.org/wiki/Butterworth_filter
Octave Forge http://octave.sf.net
Arma
, filter
, cheby1
,
ellip
, and buttord
bf = butter(4, 0.1) freqz(bf) zplane(bf)