warbleR (version 1.1.1)

compare.methods: Assessing the performance of acoustic distance measurements

Description

compare.methods create graphs to visually assess performance of acoustic distance measurements

Usage

compare.methods(X = NULL, flim = c(0, 22), bp = c(0, 22), mar = 0.1, wl = 512, ovlp = 90, 
res = 150, n = 10, length.out = 30, methods = c("XCORR", 
"dfDTW", "ffDTW", "SP"),it = "jpeg", parallel = 1)

Arguments

X

Data frame with results from manualoc function, autodetec function, or any data frame with columns for sound file name (sound.files), selection number (

flim

A numeric vector of length 2 for the frequency limit in kHz of the spectrogram, as in spectro. Default is c(0, 22).

bp

numeric vector of length 2 giving the lower and upper limits of the frequency bandpass filter (in kHz) used in the acoustic distance methods. Default is c(0, 22).

mar

Numeric vector of length 1. Specifies plot margins around selection in seconds. Default is 0.1.

wl

A numeric vector of length 1 specifying the window length of the spectrogram, default is 512.

ovlp

Numeric vector of length 1 specifying the percent overlap between two consecutive windows, as in spectro. Default is 90.

res

Numeric argument of length 1. Controls image resolution. Default is 150.

n

Numeric argument of length 1. Defines the number of plots to be produce. Default is 10.

length.out

A character vector of length 1 giving the number of measurements of fundamental or dominant frequency desired (the length of the time series). Default is 30.

methods

A character vector of length 2 giving the names of the acoustic distance methods that would be compared. The methods available are: cross-correlation (XCORR, from xcorr), dynamic time warping on dominant frequency time series (dfDTW, from

it

A character vector of length 1 giving the image type to be used. Currently only "tiff" and "jpeg" are admitted. Default is "jpeg".

parallel

Numeric. Controls whether parallel computing is applied. It specifies the number of cores to be used. Default is 1 (e.i. no parallel computing). windows OS users need to install warbleR from github to run parallel. Note that creating images

Value

• Image files with 4 spectrograms of the selection being compared and scatterplots of the acoustic space of all signals in the input data frame 'X'.

Details

This function produces graphs with spectrograms from 4 selections that allow visual inspection of the performance of acoustic distance methods at comparing those selections. The spectrograms are all plotted with the same frequency and time scales. The function compares 2 methods at a time. The methods available are: cross -correlation (XCORR, from xcorr), dynamic time warping on dominant frequency time series (dfDTW, from dtw applied on dfts output), dynamic time warping on dominant frequency time series (ffDTW, from dtw applied on ffts output), spectral parameters (SP, from specan). The graph also contains 2 scatterplots (1 for each method) of the acoustic space of all signals in the input data frame 'X'. The compared selections are randomly picked up from the pool of selections in the input data frame. The argument 'n' defines the number of comparison (e .i. graphs) to be produced. The acoustic pairwise distance between signals is shown next to the arrows linking them. The font color of a distance value correspond to the font color of the method that generetad it, as shown in the scatterplots. Distances are standardize, being 0 the distance of a signal to itself and 1 the farthest pairwise distance in the pool of signals. Principal Component Analysis (princomp) is applied to calculate distances when using spectral parameters (SP). In that case the first 2 PC's are used. Classical Multidimensional Scalling (also knwon as Principal Coordinates Analysis, (cmdscale)) is used for all other methods. Note that SP can only be used with at least 22 selections (number of rows in input data frame) as PCA only works with more units than variables. The graphs are return as image files in the working directory. The file name contains the methods being compared and the rownumber of the selections. This function uses internally a modified version of the spectro function from seewave package to create spectrograms.

Examples

# First create empty folder
setwd(tempdir())

data(list = c("Phae.long1", "Phae.long2", "Phae.long3", "Phae.long4", "manualoc.df"))
writeWave(Phae.long1,"Phae.long1.wav")
writeWave(Phae.long2,"Phae.long2.wav")
writeWave(Phae.long3,"Phae.long3.wav")
writeWave(Phae.long4,"Phae.long4.wav") 

compare.methods(X = manualoc.df, flim = c(0, 10), bp = c(0, 10), mar = 0.1, wl = 512, 
ovlp = 90, res = 200, n = 10, length.out = 30, 
methods = c("XCORR", "dfDTW"), parallel = 1, it = "tiff")

#check this folder!!
getwd()