RSEIS (version 2.1-6)

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)
###   PICK.GEN(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")