lowpass {astrochron} R Documentation

## Lowpass filter stratigraphic series

### Description

Lowpass filter stratigraphic series using rectangular, Gaussian or tapered cosine window. This function can also be used to highpass filter a record (see examples).

### Usage

lowpass(dat,padfac=2,fcut=NULL,win=0,demean=T,detrend=F,addmean=T,alpha=3,p=0.25,
xmin=0,xmax=Nyq,genplot=T,verbose=T)


### Arguments

 dat Stratigraphic series for lowpass 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. fcut Cutoff frequency for lowpass filtering. win Window type for bandpass filter: 0 = rectangular , 1= Gaussian, 2= Cosine-tapered window. 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) alpha Gaussian window parameter: alpha is 1/stdev, a measure of the width of the Dirichlet kernal. Larger values decrease the width of data window, reduce discontinuities, and increase width of the transform. Choose alpha >= 2.5. p Cosine-tapered window parameter: p is the percent of the data series tapered (choose 0-1). xmin Smallest frequency for plotting. xmax Largest frequency for plotting. genplot Generate summary plots? (T or F) verbose Verbose output? (T or F)

bandpass, 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)

# lowpass filter eccentricity terms using cosine-tapered window
lowpass_ex=lowpass(ex,fcut=.02,win=2,p=.4)

# highpass filter obliquity and precession terms using cosine-tapered window
#  if you'd like the final notch filtered record to be centered on the mean proxy