evolMTM {RSEIS} | R Documentation |
Time varying Multi-taper Spectrum (Gabor Transform)
evolMTM(a, dt = 0, numf = 1024, Ns = 0, Nov = 0, fl = 0, fh = 10)
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 |
This is a spectrogram function similar to the Gabor Transform but uses the MTM method for spectrum estimation.
List
sig |
input signal |
dt |
deltat |
wpars |
input parameters |
DSPEC |
spectrum image |
freqs |
output frequencies (y axis) |
tims |
output times (x-axis) |
Jonathan M. Lees<jonathan.lees@unc.edu>
Lees, J. M. and Park, J., 1995: Multiple-taper spectral analysis: A stand-alone C-subroutine, Computers & Geology, 21(2), 199-236.
evolfft, MTM.drive
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")