# Frequency bands plot This graphical function returns a frequency spectrum as a bar plot. ```r 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`. ## Returns 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. ## Author(s) Jerome Sueur, improved by Laurent Lellouch ## Note The value below bars is the mean between the corresponding frequency limits. ## See Also `meanspec`, `spec`, `barplot`. ## Examples ```r 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) ```

fbands function