cwt_wst | R Documentation |
This function computes the continuous wavelet transform for some families of wavelet bases: "MORLET", "DOG", "PAUL" and "HAAR". It is a translation from the Matlab(R) function published by Torrence and Compo (Torrence & Compo, 1998).
The difference between cwt_wst
and cwt
from package Rwave
is that
cwt_wst
normalizes using L^2 and cwt
uses L^1.
cwt_wst(signal, dt = 1, scales = NULL, powerscales = TRUE, wname = c("MORLET", "DOG", "PAUL", "HAAR", "HAAR2"), wparam = NULL, waverad = NULL, border_effects = c("BE", "PER", "SYM"), makefigure = TRUE, time_values = NULL, energy_density = FALSE, figureperiod = TRUE, xlab = "Time", ylab = NULL, main = NULL, zlim = NULL)
signal |
A vector containing the signal whose wavelet transform is wanted. |
dt |
Numeric. The time step of the signal. |
scales |
A vector containing the wavelet scales at wich the CWT
is computed. This can be either a vector with all the scales or, following Torrence
and Compo 1998, a vector of 3 elements with the minimum scale, the maximum scale and
the number of suboctaves per octave (in this case, |
powerscales |
Logical. It must be TRUE (default) in these cases:
|
wname |
A string, equal to "MORLET", "DOG", "PAUL", "HAAR" or "HAAR2". The difference between "HAAR" and "HAAR2" is that "HAAR2" is more accurate but slower. |
wparam |
The corresponding nondimensional parameter for the wavelet function (Morlet, DoG or Paul). |
waverad |
Numeric. The radius of the wavelet used in the computations for the cone of influence. If it is not specified, it is asumed to be √{2} for Morlet and DoG, 1/√{2} for Paul and 0.5 for Haar. |
border_effects |
String, equal to "BE", "PER" or "SYM", which indicates how to manage the border effects which arise usually when a convolution is performed on finite-lenght signals.
|
makefigure |
Logical. If TRUE (default), a figure with the wavelet power spectrum is plotted. |
time_values |
A numerical vector of length |
energy_density |
Logical. If TRUE (default), divide the wavelet power spectrum by the scales in the figure and so, values for different scales are comparable. |
figureperiod |
Logical. If TRUE (default), periods are used in the figure instead of scales. |
xlab |
A string giving a custom X axis label. |
ylab |
A string giving a custom Y axis label. If NULL (default) the Y label is
either "Scale" or "Period" depending on the value of |
main |
A string giving a custom main title for the figure. If NULL
(default) the main title is either "Wavelet Power Spectrum / Scales" or "Wavelet Power
Spectrum" depending on the value of |
zlim |
A vector of length 2 with the limits for the z-axis (the color bar). |
A list with the following fields:
coefs
: A matrix of size length(signal)
x length(scales)
,
containing the CWT coefficients of the signal.
scales
: The vector of scales.
fourierfactor
: A factor for converting scales into periods.
coi_maxscale
: A vector of length length(signal)
containing the
values of the maximum scale from which there are border effects at each time.
C. Torrence, G. P. Compo. A practical guide to wavelet analysis. B. Am. Meteorol. Soc. 79 (1998), 61–78.
dt <- 0.1 time <- seq(0, 50, dt) signal <- c(sin(pi * time), sin(pi * time / 2)) cwt <- cwt_wst(signal = signal, dt = dt, energy_density = TRUE)
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