lowpass {astrochron} | R Documentation |
Lowpass filter stratigraphic series using rectangular, Gaussian or tapered cosine window. This function can also be used to highpass filter a record (see examples).
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)
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
# 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 # value, set addmean=FALSE highpass_ex=lowpass(ex,fcut=.02,win=2,p=.4,addmean=FALSE) highpass_ex[2] <- ex[2]-highpass_ex[2] pl(2) plot(ex,type="l",main="Eccentricity+Obliquity+Precession") plot(highpass_ex,type="l",main="Obliquity+Precession highpassed signal")