specprop {seewave}R Documentation

Spectral properties

Description

This function returns a list of statistical properties of a frequency spectrum.

Usage

specprop(spec, f, str = FALSE, plot = FALSE, type = "l", ...)

Arguments

spec a data set resulting of a spectral analysis obtained with spec or meanspec (not in dB).
f sampling frequency of wave (in Hz).
str logical, if TRUE returns the results in a structured table.
plot if 1 returns the spectrum , if 2 returns the cumulative spectrum, both of them with the first quartile, the third quartile, the median and the mode plotted (by default FALSE).
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.

Details

The spectrum is converted in a probability mass function (PMF).
If a selected value has to be selected with $, the argument str has to be set to FALSE.

Value

A list of 15 values is returned

mean mean frequency (see mean)
sd standard deviation of the mean (see sd)
sem standard error of the mean
median median frequency (see median)
mad absolute deviation of median (see mad)
mode mode frequency, i.e. the dominant frequency
Q25 first quartile (see quantile)
Q75 third quartile (see quantile)
IQR interquartile range (see IQR)
cent centro�d, see note
skewness skewness, a measure of asymmetry, see note
kurtosis kurtosis, a measure of peakedness, see note
sfm spectral flatness measure (see sfm)
sh spectral entropy (see sh)
prec frequency precision of the spectrum

Note

Centroid is computed according to:

C = sum(x*y)


with:
x = frequencies, y = relative amplitude of the i frequency,
N = number of frequencies.

Skewness is computed according to:

S = sum((x-mean(x))^3)/(N-1)/sd^3

.
S < 0 when the spectrum is skewed to left,
S = 0 when the spectrum is symetric,
S > 0 when the spectrum is skewed to right.
Spectrum asymmetry increases with |S|.

Kurtosis is computed according to:

K = sum((x-mean(x))^4)/(N-1)/sd^4

.
K < 3 when the spectrum is platikurtic, i.e. it has fewer items at the center and at the tails than the normal curve but has more items in the shoulders,
K = 3 when the spectrum shows a normal shape,
K > 3 when the spectrum is leptokurtic, i.e. it has more items near the center and at the tails, with fewer items in the shoulders relative to normal distribution with the same mean and variance.

Author(s)

Jerome Sueur sueur@mnhn.fr and Caroline Simonis csimonis@mnhn.fr.

Examples

data(orni)
a<-meanspec(orni,f=22050,plot=FALSE)
specprop(a,f=22050)
# to get a single measure of the list
specprop(a,f=22050)$mode
# to get the results structured
specprop(a,f=22050,str=TRUE)
# plots
specprop(a,f=22050,plot=1)
specprop(a,f=22050,plot=2)

[Package seewave version 1.5.0 Index]