evolFFT: Time-Frequency Analysis

In jrevenaugh/TSAUMN: Time Series Analysis Tools Used in ESCI5201 at the University of Minnesota

Description

Compute evolutive spectrum using direct FFT method

Usage

evolFFT(s, deltat = 1, nfft = 1024, nwin, nstep, fl = 0,
  fh = 0.5/deltat)

Arguments

s	vector of timeseries samples or ts object. If the former, deltat should be specified, NA values are not allowed.
deltat	sampling interval of time series. Ignored if s is a ts object
nfft	length of padding window input to fft; controls frequency resolution
nwin	number of samples in fft window
nstep	number of samples to shift right between spectral estimates; controls time resolution
fl	lowest frequency to output
fh	highest frequence to output

Value

List containing the following items:

"signal"	Original input signal
"deltat"	Sampling interval of time series
"numfreqs"	Number of frequencies retained in analysis
"freqs"	Vector of frequencies retained in analysis
"wpars"	List of analysis parameters: fl, fh and nwin

Examples

require( RColorBrewer )
# create chirp signal
n <- 1024
t <- 1:n
a <- 4 * n
x <- cos( 2 * pi * t^2 / a )
# perform time-frequency analysis of chirp
evol <- evolFFT( x, deltat = 1, nwin = 200, nstep = 5 )
# plot result
plotFTSpec( evol )

jrevenaugh/TSAUMN documentation built on Nov. 8, 2019, 2:20 p.m.