fbands {seewave}

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

See Also

meanspec, spec, barplot.

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)