evolMTM: Evolutive Multi-taper Spectrum

In RSEIS: Seismic Time Series Analysis Tools

Evolutive Multi-taper Spectrum

Description

Time varying Multi-taper Spectrum (Gabor Transform)

Usage

evolMTM(a, dt = 0, numf = 1024, Ns = 0, Nov = 0, fl = 0, fh = 10)

Arguments

a	Signal
dt	Sample rate interval (s)
numf	Number of points in fft
Ns	Number of sample in sub-window
Nov	Number of sample to overlap
fl	low frequency to display
fh	high frequency to display

Details

This is a spectrogram function similar to the Gabor Transform but uses the MTM method for spectrum estimation.

Value

List

sig	input signal
dt	deltat
wpars	input parameters
DSPEC	spectrum image
freqs	output frequencies (y axis)
tims	output times (x-axis)

Author(s)

Jonathan M. Lees<[e-mail]>

References

Lees, J. M. and Park, J., 1995: Multiple-taper spectral analysis: A stand-alone C-subroutine, Computers and Geology, 21(2), 199-236.

See Also

evolfft, MTM.drive

Examples

data(KH)
###   swig(KH)

Xamp <- KH$JSTR[[1]]

dt <- KH$dt[1]
plot(seq(from=0, length=length(Xamp), by=dt), Xamp, type='l')
##  limit the trace, somewhat
Xamp <- Xamp[12670:22669]
plot(seq(from=0, length=length(Xamp), by=dt), Xamp, type='l')


Nfft<-4096   ###  fft length
Ns<-512      ###  number of samples in a window
Nov<-480    ###  number of samples of overlap per window
fl<-0        ###  low frequency to return
fh<-12     ###  high frequency to return

EV <- evolMTM(Xamp, dt = dt, numf = Nfft, Ns = Ns, Nov = Nov, fl = fl, fh
= fh)


PE <- plotevol(EV, log=1, fl=0.01, fh=fh, col=rainbow(100), ygrid=FALSE,
STAMP="", STYLE="ar")


##   compare with:
## EVf <- evolfft(Xamp, dt = dt, Nfft =Nfft , Ns =Ns , Nov =Nov , fl =fl, fh = fh)

##  PE <- plotevol(EVf, log=1, fl=fl, fh=fh, col=rainbow(100), ygrid=FALSE,STAMP="", STYLE="fft")

RSEIS documentation built on Sept. 13, 2024, 1:09 a.m.