seewave (version 1.0)

spectro: 2D-spectrogram of a time wave

Description

This functions returns a two-dimension spectrographic representation of a time wave. The function corresponds to short-term Fourier transform. An amplitude contour plot can be overlaid.

Usage

spectro(wave, f, wl, zp = 0, ovlp = 0, plot = TRUE,
grid = TRUE, osc = FALSE, scale = TRUE, cont = FALSE,
collevels = seq(-30, 0, 1), palette = spectro.colors,
contlevels = seq(-30, 0, 10), colcont = "black", colgrid = "black",
plot.title = title(main = "", xlab = "Time (s)",
ylab = "Frequency (kHz)"), scalelab = "Amplitude
(dB)",
scalefontlab = 1, axisX = TRUE, axisY = TRUE,
...)

Arguments

wave

data describing a time wave.

f

sampling frequency of wave.

wl

length of the window for the analysis (even number of points).

zp

zero-padding (even number of points), see Details.

ovlp

overlap between two successive windows (in %).

plot

logical, if TRUE plots the spectrogram (by default TRUE).

grid

logical, if TRUE plots a y-axis grid (by default TRUE).

osc

logical, if TRUE plots an oscillogram beneath the spectrogram (by default FALSE).

scale

logical, if TRUE plots a dB colour scale on the right side of the spectrogram (by default TRUE).

cont

logical, if TRUE overplots contour lines on the spectrogram (by default FALSE).

collevels

a set of levels which are used to partition the amplitude range of the spectrogram (in dB).

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.

colgrid

colour for grid plotting.

plot.title

statements which add titles to the plot.

scalelab

amplitude scale label.

scalefontlab

font of the amplitude scale label.

axisX

logical, if TRUE plots X-axis (by default TRUE).

axisY

logical, if TRUE plots Y-axis (by default TRUE).

...

other contour and oscillo graphical parameters.

Value

• If plot is FALSE, this function returns a matrix. Each column corresponds to a Fourier transform of length wl.

Details

A Hanning function is applied to the analysis window. zp adds 0 values on both sides of the analysis window. This increases frequency resolution without altering time resolution. Any colour palette can be used. In particular, it is possible to use other palettes coming with seewave: rev.heat.colors, rev.terrain.colors, rev.topo.colors, rev.cm.colors corresponding to the reverse of heat.colors, terrain.colors, topo.colors, cm.colors. Use locator to identify points.

References

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

See Also

spectro3D, oscillo, dBscale, fft.

Examples

data(tico)
data(peewit)
data(pellucens)
data(alauda)
# simple plots
spectro(tico,f=22050,wl=512)
spectro(tico,f=22050,wl=512,osc=TRUE)
spectro(tico,f=22050,wl=512,scale=FALSE)
spectro(tico,f=22050,wl=512,osc=TRUE, scale=FALSE)
# manipulating wl
op<-par(mfrow=c(2,2))
spectro(tico,f=22050,wl=256,scale=FALSE)
title("wl = 256")
spectro(tico,f=22050,wl=512,scale=FALSE)
title("wl = 512")
spectro(tico,f=22050,wl=1024,scale=FALSE)
title("wl = 1024")
spectro(tico,f=22050,wl=4096,scale=FALSE)
title("wl = 4096")
par(op)
# manipulating ovlp
op<-par(mfrow=c(2,1))
spectro(alauda,f=22050,wl=512,scale=FALSE)
title("ovlp = 0")
spectro(alauda,f=22050,wl=512,ovlp=95,scale=FALSE)
title("ovlp = 95")
par(op)
# a full plot
pellu2<-cutw(pellucens,f=22050,from=1,to=nrow(pellucens)/22050,plot=FALSE)
spectro(pellu2,f=22050,wl=512,ovlp=85,zp=16,osc=TRUE,
    cont=TRUE,contlevels=seq(-30,0,20),colcont="red",
    lwd=1.5,lty=2,palette=rev.terrain.colors)
# black and white spectrogram 
spectro(pellu2,f=22050,wl=512,ovlp=85,zp=16,
    palette=rev.gray.colors)
# colour modifications
spectro(pellu2,f=22050,wl=512,ovlp=85,zp=16,
palette=rev.cm.colors,osc=TRUE,colwave="orchid1") 
op<-par(bg="black",col="white")
spectro(pellu2,f=22050,wl=512,ovlp=85,zp=16,osc=TRUE,palette=rev.heat.colors,
colgrid="white", colwave="white",colaxis="white",collab="white",
colline="white")
par(op)