ChemoSpec (version 4.2.8)

surveySpectra: Plot Measures of Central Tendency and Spread for a Spectra Object

Description

These functions compute and plot various measures of central tendency and spread for a "Spectra" object. Several different measures/spreads are available. These are useful as an overview of where a data set varies the most.

Usage

surveySpectra(spectra, method = c("sd", "sem", "sem95", "mad", "iqr"),
by.gr = TRUE, ...)
surveySpectra2(spectra, method = c("sd", "sem", "sem95", "mad", "iqr"),
lab.pos = 0.9*max(spectra$freq), ...)

Value

None; side effect is a plot

Details

For surveySpectra the method choice works as follows: sd plots the mean spectrum +/- the standard deviation, sem plots the mean spectrum +/- the standard error of the mean, sem95 plots the mean spectrum +/- the standard error at the 95 percent confidence interval, mad plots the median spectrum +/- the median absolute deviation, and finally, iqr plots the median spectrum + the upper hinge and - the lower hinge.

For surveySpectra2, the spectra are mean centered and plotted. Below that, the relative summary statistic is plotted, offset, but on the same scale.

References

https://github.com/bryanhanson/ChemoSpec

Examples

data(SrE.IR)
myt <- expression(bolditalic(Serenoa)~bolditalic(repens)~bold(Extract~IR~Spectra))
surveySpectra(SrE.IR, method = "iqr", main = myt)
surveySpectra2(SrE.IR, method = "iqr", main = myt)