seewave (version 1.4.3)

covspectro: Covariance between two spectrograms

Description

This function tests the similarity between two spectrograms by returning their maximal covariance and the time shift related to it.

Usage

covspectro(wave1, wave2, f, wl = 512, wn = "hanning", n, plot = TRUE, plotval = TRUE,
method = "spearman", col = "black", colval = "red", cexval = 1,
fontval = 1, xlab = "Time (s)",
ylab = "Normalised covariance (cov)", type = "l", ...)

Arguments

wave1

data or a Sample object generated loading a wav file with loadSample (package Sound) describing a first time wave.

wave2

data or a Sample object generated loading a wav file with loadSample (package Sound) describing a second time wave.

f

sampling frequency of wave1 and wave1 (in Hz). Does not need to be specified if wave1 and/or wave2 are/is (a) Sample object(s).

wl

length of the window for the analysis (even number of points, by default = 512).

wn

window name, see ftwindow (by default "hanning").

n

number of covariances computed between wave1 and wave2 when sliding wave2 along wave1.

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).

...

other plot graphical parameters.

Value

• If plot is FALSE, covspectro returns a list containing three components:
• cov
  the successive covariance values between wave1 and wave2.
• covmax
  the maximum covariance between wave1 and wave2.
• t
  the time offset corresponding to cov.

Details

Successive covariances between the spectrogram of wave1 and the spectrogram of wave2 are computed when regularly sliding forward and backward wave2 along wave1. The maximal covariance is obtained at a particular shift (time offset). This shift may be positive or negative. n sets in how many steps wave2will be slided along wave1. Time process can be then decreased by setting low n value. Inverting wave1 and wave2 may give slight different results.

References

Hopp, S. L., Owren, M. J. and Evans, C. S. (Eds) 1998. Animal acoustic communication. Springer, Berlin, Heidelberg.

See Also

corspec, corenv, spectro, cor,

Examples

# covariance between two echemes of a cicada calling song
data(orni)
orni1<-cutw(orni,f=22050,from=0,to=0.1,plot=FALSE)
orni2<-cutw(orni,f=22050,from=0.15,to=0.25,plot=FALSE)
covspectro(orni1,orni2,f=22050,n=37)