R: Frequency bands plot

fbands {seewave}

R Documentation

Frequency bands plot

Description

This graphical function returns a frequency spectrum as a bar plot.

Usage

fbands(spec, f = NULL, bands = 10, width = FALSE, mel = FALSE, plot = TRUE,
xlab = NULL, ylab = "Relative amplitude", ...)

Arguments

`spec`	a data set resulting of a spectral analysis obtained with `spec` or `meanspec`. Can be in dB.
`f`	sampling frequency of `spec` (in Hz). Not requested if the first column of `spec` contains the frequency axis.
`bands`	a numeric vector. If vector of length 1, then sets the number of bands dividing in equal parts the spectrum. If of length > 1, then takes the values as kHz limits of the bands dividing the spectrum. These bands can be of different size. See details and examples.
`width`	logical, if `TRUE` and that `bands` is an irregular series of values, then the width of the bands will be proportional to the frequency limits defined in `bands`.
`mel`	a logical, if `TRUE` the (htk-)mel scale is used.
`plot`	logical, if `TRUE`, a plot showing the peaks is returned.
`xlab`	label of the x-axis.
`ylab`	label of the y-axis.
`...`	other `plot` graphical parameters.

Details

The function proceeds as follows

divides the spectrum in bands. The limits of the bands are set with the argument bands. There are two options:
- you set a number of bands with equal size by giving a single value to bands. For instance, setting bands to a value of 10 will slice the spectrum in 10 equal parts and return 10 local peaks.
- you set the limits of the bands. This is achieve by giving a numeric vector to bands. The limits can follow a regular or irregular series. For instance attributing the vector c(0,2,4,8) will generate the following bands [0,2[, [2,4[, [4,8] kHz. Be aware that the last value should not exceed half the sampling frequency used to obtain the spectrum spec.
uses the function barplot.

Value

A two-column matrix, the first column corresponding to the frequency values (x-axis, mean of the bars limits) and the second column corresponding to height values (y-axis) of the bars.

Note

The value below bars is the mean between the corresponding frequency limits.

Author(s)

Jerome Sueur, improved by Laurent Lellouch

Examples

data(sheep)
spec <- meanspec(sheep, f=8000, plot=FALSE)
# default plot
fbands(spec)
# setting a specific number of bands
fbands(spec, bands=6)
#setting specific regular bands limits
fbands(spec, bands=seq(0,4,by=0.25))
# some plot tuning
op <- par(las=1)
fbands(spec, bands=seq(0,4,by=0.1),
       horiz=TRUE, col=heat.colors(41),
       xlab="", ylab="",
       cex.axis=0.75, cex.names = 0.75,
       axes=FALSE)
par(op)
# showing or not the width of the bands
oct <- octaves(440,3)/1000
op <- par(mfrow=c(2,1))
fbands(spec, bands=oct, col="blue")
fbands(spec, bands=oct, width = TRUE, col="red")
par(op)
# kind of horizontal zoom
op <- par(mfrow=c(2,1))
fbands(spec, bands=seq(0,4,by=0.2), col=c(rep(1,10),
   rep("orange",5),rep(1,5)), main="all frequency range")
fbands(spec, bands=seq(2,3,by=0.2),
   col="orange", main="a subset or zoom in")
par(op)
# kind of dynamic frequency bands
specs <- dynspec(sheep, f=8000, plot= FALSE)$amp
out <- apply(specs, f=8000, MARGIN=2,
     FUN = fbands, bands = seq(0,4,by=0.2),
     col = 1, ylim=c(0,max(specs)))
# mel scale
require(tuneR)
mel <- melfcc(sheep, nbands = 256, dcttype = "t3", fbtype = "htkmel", spec_out=TRUE)
melspec.mean <- apply(mel$aspectrum, MARGIN=2, FUN=mean)
melspec.mean <- melspec.mean/max(melspec.mean) # [0,1] scaling 
fbands(melspec.mean, f=8000, bands=8)

[Package seewave version 2.1.6 Index]