windowed_scale_index: Windowed scale index

Description Usage Arguments Value References Examples

View source: R/windowed_scale_index.R

Description

This function computes the windowed scale indices of a signal in the scale interval [s_0,s_1], for a given set of scale parameters s_1 and taking s_0 as the minimum scale (see Ben<c3><ad>tez et al. 2010).

The windowed scale index of a signal in the scale interval [s_0,s_1] centered at time tc and with time windows radius windowrad is given by the quotient

WS_{windowrad} (tc,s_{min})/WS_{windowrad}(tc,s_{max}),

where WS_{windowrad} is the corresponding windowed scalogram with time windows radius windowrad, s_{max} \in [s_0,s_1] is the smallest scale such that WS_{windowrad}(tc,s)≤ WS_{windowrad}(tc,s_{max}) for all s \in [s_0,s_1], and s_{min} \in [s_{max},2s_1] is the smallest scale such that WS_{windowrad}(tc,s_{min})≤ WS_{windowrad}(tc,s) for all s \in [s_{max},2s_1].

Usage

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windowed_scale_index(signal,
                            dt = 1,
                            scales = NULL,
                            powerscales = TRUE,
                            s1 = NULL,
                            windowrad = NULL,
                            delta_t = NULL,
                            wname = c("MORLET", "DOG", "PAUL", "HAAR", "HAAR2"),
                            wparam = NULL,
                            waverad = NULL,
                            border_effects = c("BE", "INNER", "PER", "SYM"),
                            makefigure = TRUE,
                            time_values = NULL,
                            figureperiod = TRUE,
                            xlab = "Time",
                            ylab = NULL,
                            main = "Windowed Scale Index")

Arguments

signal

A vector containing the signal whose windowed scale indices are wanted.

dt

Numeric. The time step of the signal.

scales

A vector containing the wavelet scales at wich the windowed scalograms are computed. This can be either a vector with all the scales, or (if powerscales is TRUE) following Torrence and Compo 1998, a vector of three elements with the minimum scale, the maximum scale and the number of suboctaves per octave. If NULL, they are automatically computed.

powerscales

Logical. If TRUE (default), construct power 2 scales from scales. If scales is NULL, they are automatically computed.

s1

A vector containing the scales s_1. The windowed scale indices are computed in the intervals [s_0,s_1], where s_0 is the minimum scale in scales.

windowrad

Integer. Time radius for the windows, measured in dt. By default, it is set to ceiling(length(signal) / 20).

delta_t

Integer. Increment of time for the construction of windows central times, measured in dt. By default, it is set to ceiling(length(signal) / 256).

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

A string, equal to "BE", "INNER", "PER" or "SYM", which indicates how to manage the border effects which arise usually when a convolution is performed on finite-lenght signals.

  • "BE": With border effects, padding time series with zeroes.

  • "INNER": Normalized inner scalogram with security margin adapted for each different scale.

  • "PER": With border effects, using boundary wavelets (periodization of the original time series).

  • "SYM": With border effects, using a symmetric catenation of the original time series.

makefigure

Logical. If TRUE (default), a figure with the windowed scale indices is plotted.

time_values

A numerical vector of length length(signal) containing custom time values for the figure. If NULL (default), it will be computed starting at 0.

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 "s1" or "Period of s1" depending on the value of figureperiod if length(s1) > 1, or "Windowed Scale Index" if length(s1) == 1.

main

A string giving a custom main title for the figure.

Value

A list with the following fields:

References

R. Ben<c3><ad>tez, V. J. Bol<c3><b3>s, M. E. Ram<c3><ad>rez. A wavelet-based tool for studying non-periodicity. Comput. Math. Appl. 60 (2010), no. 3, 634-641.

Examples

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dt <- 0.1
time <- seq(0, 50, dt)
signal <- c(sin(pi * time), sin(pi * time / 2))
# First, we try with default s1 scales (a vector with a wide range of values for s1).
wsi_full <- windowed_scale_index(signal = signal, dt = dt, figureperiod = FALSE)
# Next, we choose a meaningful s1 value, greater than all relevant scales.
wsi <- windowed_scale_index(signal = signal, dt = dt, s1 = 4, figureperiod = FALSE)

wavScalogram documentation built on May 24, 2019, 5:03 p.m.