RSEIS (version 4.2-4)

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)

Value

List

sig

input signal

dt

deltat

wpars

input parameters

DSPEC

spectrum image

freqs

output frequencies (y axis)

tims

output times (x-axis)

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

Author

Jonathan M. Lees<[e-mail]>

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 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")