evolfft {RSEIS}R Documentation

Spectrogram fft

Description

Spectrogram using simple fft (Gabor Transform)

Usage

evolfft(a, dt = 0, Nfft = 0, Ns = 0, Nov = 0, fl = 0, fh = 10)

Arguments

a signal
dt sample rate interval (s)
Nfft 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 duplication of the spectrogram function in matlab which applies Welsh's Method.

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.edu>

See Also

evolMTM, evolAR, MTM.drive

Examples


data(CE1)

####  plot signals
plot(CE1$x, CE1$y, type='l')

###  set parameters
Nfft=1024   ###  fft length
Ns=250      ###  number of samples in a window
Nov=240     ###  number of samples of overlap per window
fl=0        ###  low frequency to return
fh=1/(2*CE1$dt)     ###  high frequency to return

########  calculate the evolutive fft (Gabor Transform)
EV = evolfft(CE1$y, dt =CE1$dt , Nfft = Nfft, Ns =Ns , Nov =Nov , fl =fl
, fh = 25)

### plot image, but it does not look too interesting
image(EV$DSPEC)

### plot Gabor transform with special function
PE = plotevol(EV, log=0, fl=0.01, fh=100, col=rainbow(100), ygrid=FALSE,
STAMP="", STYLE="fft")


[Package RSEIS version 2.1-4 Index]