bandpass {astrochron} | R Documentation |
Bandpass filter stratigraphic series
Description
Bandpass filter stratigraphic series using rectangular, Gaussian or tapered cosine (a.k.a. Tukey) window. This function can also be used to notch fiter a record (see examples).
Usage
bandpass(dat,padfac=2,flow=NULL,fhigh=NULL,win=0,alpha=3,p=0.25,demean=T,
detrend=F,addmean=T,output=1,xmin=0,xmax=Nyq,genplot=T,verbose=T)
Arguments
dat |
Stratigraphic series for bandpass filtering. First column should be location (e.g., depth), second column should be data value. |
padfac |
Pad with zeros to (padfac*npts) points, where npts is the original number of data points. |
flow |
Lowest frequency to bandpass. |
fhigh |
Highest frequency to bandpass. |
win |
Window type for bandpass filter: 0 = rectangular , 1= Gaussian, 2= Cosine-tapered window (a.k.a. Tukey window). |
alpha |
Gaussian window parameter: alpha is 1/stdev, a measure of the width of the Dirichlet kernel. Choose alpha >= 2.5. |
p |
Cosine-tapered (Tukey) window parameter: p is the percent of the data series tapered (choose 0-1). |
demean |
Remove mean from data series? (T or F) |
detrend |
Remove linear trend from data series? (T or F) |
addmean |
Add mean value to bandpass result? (T or F) |
output |
Output: (1) filtered series, (2) bandpass filter window. |
xmin |
Smallest frequency for plotting. |
xmax |
Largest frequency for plotting. |
genplot |
Generate summary plots? (T or F) |
verbose |
Verbose output? (T or F) |
Value
bandpassed stratigraphic series.
See Also
lowpass
, noKernel
, noLow
, prewhiteAR
, prewhiteAR1
, and taner
Examples
# generate example series with periods of 405 ka, 100 ka, 40ka, and 20 ka, plus noise
ex=cycles(freqs=c(1/405,1/100,1/40,1/20),end=1000,dt=5,noisevar=.1)
# bandpass precession term using cosine-tapered window
bandpass_ex <- bandpass(ex,flow=0.045,fhigh=0.055,win=2,p=.4)
# notch filter (remove) obliquity term using cosine-tapered window
# if you'd like the final notch filtered record to be centered on the mean proxy
# value, set addmean=FALSE
notch_ex <- bandpass(ex,flow=0.02,fhigh=0.03,win=2,p=.4,addmean=FALSE)
notch_ex[2] <- ex[2]-notch_ex[2]
pl(2)
plot(ex,type="l",main="Eccentricity+Obliquity+Precession")
plot(notch_ex,type="l",main="Following application of obliquity notch filter")