astrochron (version 1.4)

tanerFC: Apply Taner bandpass or lowpass filter to Fourier coefficients

Description

Apply Taner bandpass or lowpass filter to Fourier coefficients.

Usage

tanerFC(fc,npts,flow=NULL,fhigh=NULL,roll=10^3,output=1,genplot=T,verbose=T)

Value

bandpassed stratigraphic series.

Arguments

fc

Fourier coefficients, as output by the function 'periodogram'. The first column is frequency, the second column contains the real coefficients, and the third column contains the imaginary coefficients.

npts

The number of points in the stratigraphic series used to estimate the Fourier coefficients.

flow

Low frequency cut-off for Taner filter (half power point). If this value is not set (NULL), it will default to -1*fhigh, which will create a lowpass filter.

fhigh

High frequency cut-off for Taner filter (half power point).

roll

Roll-off rate, in dB/octave. Typical values are 10^3 to 10^12, but can be larger.

output

Output: (1) filtered series, (2) bandpass filter window.

genplot

Generate summary plots? (T or F)

verbose

Verbose output? (T or F)

Details

This function is designed for cases when one needs to efficiently apply a range of filter parameters to a stratigraphic series. It is used within function 'timeOpt' to speed up processing. For more general use, function 'taner' is preferred, which also provides a range of plots for evaluating the filtering.

Fourier coefficients for 'tanerFC' can be determined with the function 'periodogram', using options 'output=2' and 'nrm=0'.

References

http://www.rocksolidimages.com/pdf/attrib_revisited.htm#_Toc328470897

See Also

bandpass, lowpass, noKernel, noLow, prewhiteAR, and prewhiteAR1

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)

# calculate the Fourier coefficients using periodogram function. this must be done with 
# no normalization (nrm=0)
fc_ex <- periodogram(ex,demean=TRUE,output=2,nrm=0)

# bandpass precession term using Taner window 
bandpass_ex <- tanerFC(fc=fc_ex,npts=201,flow=0.045,fhigh=0.055,roll=10^10)

# lowpass filter eccentricity terms using Taner window
lowpass_ex <- tanerFC(fc=fc_ex,npts=201,fhigh=.02,roll=10^10)