bandpass {astrochron}

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")