R: Continuous coherence function between two time waves

ccoh {seewave}

R Documentation

Continuous coherence function between two time waves

Description

This function returns a two-dimension coherence representation between two time waves. The function corresponds to a sliding coherence function along the two signals. This produces a 2-D density plot. An amplitude contour plot can be overlaid.

Usage

ccoh(wave1, wave2, f, channel = c(1,1), wl = 512, ovlp = 0, plot = TRUE,
grid = TRUE, scale = TRUE, cont = FALSE,
collevels = seq(0, 1, 0.01), palette = reverse.heat.colors,
contlevels = seq(0, 1, 0.01), colcont = "black",
colbg="white", colgrid = "black",
colaxis = "black", collab="black",
xlab = "Time (s)", ylab = "Frequency (kHz)",
scalelab = "Coherence",
main = NULL,
scalefontlab = 1, scalecexlab =0.75, axisX = TRUE, axisY = TRUE,
flim = NULL, flimd = NULL,
...)

Arguments

`wave1`	a first R object
`wave2`	a second R object
`f`	sampling frequency of `wave` (in Hz). Does not need to be specified if embedded in `wave`.
`channel`	channel of the R objects, by default left channel (1) for each object.
`wl`	window length for the analysis (even number of points, by default = 512).
`ovlp`	overlap between two successive windows (in %).
`plot`	logical, if `TRUE` plots the continuous coherence function (by default `TRUE`).
`grid`	logical, if `TRUE` plots a y-axis grid (by default `TRUE`).
`scale`	logical, if `TRUE` plots a dB colour scale on the right side of the plot (by default `TRUE`).
`cont`	logical, if `TRUE` overplots contour lines on the plot (by default `FALSE`).
`collevels`	a set of levels which are used to partition the amplitude range of the coherence (should be between 0 and 1.
`palette`	a color palette function to be used to assign colors in the plot, see `Details`.
`contlevels`	a set of levels which are used to partition the amplitude range for contour overplot (in dB).
`colcont`	colour for `cont` plotting.
`colbg`	background colour.
`colgrid`	colour for `grid` plotting.
`colaxis`	color of the axes.
`collab`	color of the labels.
`xlab`	label of the time axis.
`ylab`	label of the frequency axis.
`scalelab`	label fo the amplitude scale.
`main`	label of the main title.
`scalefontlab`	font of the amplitude scale label.
`scalecexlab`	cex of the amplitude scale label.
`axisX`	logical, if `TRUE` plots time X-axis (by default `TRUE`).
`axisY`	logical, if `TRUE` plots frequency Y-axis (by default `TRUE`).
`flim`	modifications of the frequency Y-axis limits.
`flimd`	dynamic modifications of the frequency Y-axis limits. New `wl` and `ovlp` arguments are applied to increase time/frequency resolution.
`...`	other `contour` and `oscillo` graphical parameters.

Details

Coherence is a frequency domain function computed to show the degree of a relationship between two signals. The value of the coherence function ranges between zero and one, where a value of zero indicates there is no causal relationship between the signals. A value of one indicates the existence of linear frequency response between the two signals. This can be used, for instance, to compare the input and output signals of a system.
Any colour palette can be used. In particular, it is possible to use other palettes coming with seewave: temp.colors, reverse.gray.colors.1, reverse.gray.colors.2, spectro.colors, reverse.terrain.colors, reverse.topo.colors, reverse.cm.colors corresponding to the reverse of terrain.colors, topo.colors, cm.colors.
Use locator to identify points.

Value

This function returns a list of three items:

`time`	a numeric vector corresponding to the time axis.
`freq`	a numeric vector corresponding to the frequency axis.
`amp`	a numeric matrix corresponding to the coherence. Each column corresponds to a coherence function of length `wl`.

Note

This function is based on spec.pgram, contour and filled.contour. See spectro for graphical changes.

Author(s)

Jerome Sueur sueur@mnhn.fr but this function is mainly based on spec.pgram by Martyn Plummer, Adrian Trapletti and B.D. Ripley

Examples

wave1<-synth(d=1,f=4000,cf=500)
wave2<-synth(d=1,f=4000,cf=800)
ccoh(wave1,wave2,f=4000)

[Package seewave version 2.1.6 Index]