R: Median of the amplitude envelope

M {seewave}

R Documentation

Median of the amplitude envelope

Description

This function computes an acoustic index based on the median of the amplitude envelope.

Usage

M(wave, f, channel = 1, envt = "hil", plot = FALSE, ...)

Arguments

`wave`	an `R` object.
`f`	sampling frequency of wave (in Hz). Does not need to be specified if embedded in `wave`.
`channel`	channel of the R object, by default left channel (1).
`envt`	the type of envelope to be used: either `"abs"` for absolute amplitude envelope or `"hil"` for Hilbert amplitude envelope. See `env`.
`plot`	logical, if TRUE returns a plot of the amplitude envelope of wave (by default `FALSE`).
`...`	other env parameters, in particular smoothing parameters. See `env`.

Details

This amplitude index M is computed according to:

M = median(A(t)) * 2^{1-depth}

with

0 <= M <= 1

where A(t) is the amplitude envelope and depth is the signal digitization depth in number of bits.

Value

A numeric vector of length 1 between 0 and 1, without unit.

Author(s)

Jerome Sueur and Marion Depraetere

References

Depraetere M, Pavoine S, Jiguet F, Gasc A, Duvail S, Sueur J (2012) Monitoring animal diversity using acoustic indices: implementation in a temperate woodland. Ecological Indicators, 13, 46-54.

Examples

data(tico)
M(tico)
# smoothing the amplitude may change slightly the result
M(tico, msmooth=c(500,50), plot=TRUE)

[Package seewave version 2.1.6 Index]