bandpass: Bandpass filter stratigraphic series

In astrochron: A Computational Tool for Astrochronology

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")

astrochron documentation built on Sept. 30, 2024, 9:14 a.m.