RSEIS (version 3.5-2)

evolMTM: 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

Value

List

sig

input signal

dt

deltat

wpars

input parameters

DSPEC

spectrum image

freqs

output frequencies (y axis)

tims

output times (x-axis)

Details

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

References

Lees, J. M. and Park, J., 1995: Multiple-taper spectral analysis: A stand-alone C-subroutine, Computers \& 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")