R: Plot Measures of Central Tendency and Spread for a Spectra...

surveySpectra {ChemoSpec} | R Documentation

## Plot Measures of Central Tendency and Spread for a Spectra Object

### Description

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), ...)

### Arguments

`spectra` | An object of S3 class `Spectra` to be analyzed.
`method` | Character. One of `c("sd", "sem", "sem95", "mad", "iqr")`.
`by.gr` | Logical, indicating if the analysis is to be done by group or not. Applies to `surveySpectra` only.
`...` | Additional parameters to be passed to the plotting routines.
`lab.pos` | Numeric, giving the frequency where the label should be drawn. Applies to `surveySpectra2` only.

### 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.

### Value

None; side effect is a plot

### Functions

- `surveySpectra`: Spectral survey emphasizing mean or median spectrum, optionally by group.

- `surveySpectra2`: Spectral survey emphasizing variation among spectra.

### Author(s)

Bryan A. Hanson, DePauw University.

### 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)

[Package ChemoSpec version 4.4.97 Index]