| bwfilter {seewave} | R Documentation |
This function is a Butterworth frequency filter that filters out a selected frequency section of of a time wave (low-pass, high-pass, low-stop, high-stop, bandpass or bandstop frequency filter).
bwfilter(wave, f, channel = 1, n = 1, from = NULL, to = NULL, bandpass = TRUE, listen = FALSE, output = "matrix")
wave |
an R object. |
f |
sampling frequency of |
channel |
channel of the R object, by default left channel (1). |
n |
Order of the filter. See details. |
from |
start frequency (in Hz) where to apply the filter. |
to |
end frequency (in Hz) where to apply the filter. |
bandpass |
if |
listen |
if |
output |
character string, the class of the object to return, either
|
The order of the filter determines the value of the roll-off value, that is the dB decrease per octave of the transfer function. A filter of order n will have a transfer function with a roll-off value of - n*6 dB.
A new wave is returned. The class
of the returned object is set with the argument output.
This function mainly uses the functions filter() and
filtfilt() from the package signal
Jerome Sueur, functions filter() and
filtfilt() from the package signal.
Stoddard, P. K. (1998). Application of filters in bioacoustics. In: Hopp, S. L., Owren, M. J. and Evans, C. S. (Eds), Animal acoustic communication. Springer, Berlin, Heidelberg,pp. 105-127.
ffilter, bwfilter, preemphasis, lfs, afilter
require(signal) f <- 8000 a <- noisew(f=f, d=1) ## low-pass # 1st order filter res <- bwfilter(a, f=f, n=1, to=1500) # 8th order filter res <- bwfilter(a, f=f, n=8, to=1500) ## high-pass res <- bwfilter(a, f=f, from=2500) ## band-pass res <- bwfilter(a, f=f, from=1000, to=2000) ## band-stop res <- bwfilter(a, f=f, from=1000, to=2000,bandpass=FALSE)