seewave (version 1.7.6)

corenv: Cross-correlation between two time wave envelopes

Description

This function tests the similarity between two time wave envelopes by returning their maximal correlation and the time shift related to it.

Usage

corenv(wave1, wave2, f, envt="hil", msmooth = NULL, ksmooth = NULL,
plot = TRUE, plotval = TRUE,
method = "spearman", col = "black", colval = "red",
cexval = 1, fontval = 1, xlab = "Time (s)",
ylab = "Coefficient of correlation (r)", type = "l", pb = FALSE, ...)

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.

envt

the type of envelope to be used: either "abs" for absolute amplitude envelope or "hil" for Hilbert amplitude envelope. See env.

msmooth

a vector of length 2 to smooth the amplitude envelope with a mean sliding window. The first component is the window length (in number of points). The second component is the overlap between successive windows (in %). See

ksmooth

kernel smooth via kernel. See env.

plot

logical, if TRUE plots r values against frequency shift (by default TRUE).

plotval

logical, if TRUE adds to the plot maximum r value and frequency offset (by default TRUE).

method

a character string indicating which correlation coefficient is to be computed ("pearson", "spearman", or "kendall") (see cor).

col

colour of r values.

colval

colour of r max and frequency offset values.

cexval

character size of r max and frequency offset values.

fontval

font of r max and frequency offset values.

xlab

title of the frequency axis.

ylab

title of the r axis.

type

if plot is TRUE, type of plot that should be drawn. See plot for details (by default "l" for lines).

pb

if TRUE returns a text progress bar in the console.

...

other plot graphical parameters.

Value

• If plot is FALSE, corenv returns a list containing four components:
• r
  a two-column matrix, the first colum corresponding to the time shift (frequency x-axis) and the second column corresponding to the successive r correlation values between env1 and env2 (correlation y-axis).
• rmax
  the maximum correlation value between x and y.
• p
  the p value corresponding to rmax.
• t
  the time offset corresponding to rmax.

Details

Successive correlations between the envelopes of wave1 and wave2 are computed when regularly sliding forward and backward wave2 along wave1. The maximal correlation is obtained at a particular shift (time offset). This shift may be positive or negative. The higher smooth is set up, the faster will be the computation but less precise the results will be. The corresponding p value, obtained with cor.test, is plotted. Inverting wave1 and wave2 may give slight different results.

See Also

env,corspec,covspectro, cor,cor.test.

Examples

data(orni)
# cross-correlation between two echemes of a cicada song
wave1<-cutw(orni,f=22050,from=0.3,to=0.4,plot=FALSE)
wave2<-cutw(orni,f=22050,from=0.58,to=0.68,plot=FALSE)
corenv(wave1,wave2,f=22050)