R: Evolutive Multi-taper Spectrum

evolMTM {RSEIS} | R Documentation

## 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<jonathan.lees@unc.edu>

### 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")

[Package RSEIS version 3.7-4 Index]