wl2i: Conversion between Wavelength and Spectra Matrix Column Index...

In hyperSpec: Work with Hyperspectral Data, i.e. Spectra + Meta Information (Spatial, Time, Concentration, ...)

Description

If wavelength is numeric, each of its elements is converted to the respective index. Values outside the range of x@wavelength become NA.

Usage

wl2i(x, wavelength = stop("wavelengths are required."))

i2wl(x, i)

Arguments

x	a hyperSpec object
wavelength	the wavelengths to be converted into column indices, either numeric or a formula, see details.
i	the column indices into the spectra matrix for which the wavelength is to be computed

Details

If the range is given as a formula (i.e. start ~ end, a sequence

index corresponding to start : index corresponding to end

is returned. If the wavelengths are not ordered, that may lead to chaos. In this case, call orderwl first.

Two special variables can be used: min and max, corresponding to the lowest and highest wavelength of x, respectively.

start and end may be complex numbers. The resulting index for a complex x is then

index (Re (x)) + Im (x)

Value

A numeric containing the resulting indices for wl2i

i2wl returns a numeric with the wavelengths

Author(s)

C. Beleites

Examples

flu
wl2i (flu, 405 : 407)
wl2i (flu, 405 ~ 407)

## beginning of the spectrum to 407 nm
wl2i (flu, min ~ 407)

## 2 data points from the beginning of the spectrum to 407 nm
wl2i (flu, min + 2i ~ 407)

## the first 3 data points
wl2i (flu, min ~ min + 2i)

## from 490 nm to end of the spectrum
wl2i (flu, 490 ~ max)

## the last 8 data points
wl2i (flu, max - 7i ~ max)

## get 450 nm +- 3 data points
wl2i (flu, 450 - 3i ~ 450 + 3i)

wl2i (flu, 300 : 400) ## all NA:
wl2i (flu, 600 ~ 700) ## NULL: completely outside flu's wavelength range
i2wl (chondro, 17:20)

Example output

Loading required package: lattice
Loading required package: grid
Loading required package: ggplot2
Package hyperSpec, version 0.99-20180627

To get started, try
   vignette ("hyperspec")
   package?hyperSpec 
   vignette (package = "hyperSpec")

If you use this package please cite it appropriately.
   citation("hyperSpec")
will give you the correct reference.

The project homepage is http://hyperspec.r-forge.r-project.org


hyperSpec object
   6 spectra
   3 data columns
   181 data points / spectrum
wavelength: lambda/nm [numeric] 405.0 405.5 ... 495 
data:  (6 rows x 3 columns)
   1. spc: I[fl]/"a.u." [matrix181] 27.15000 66.80133 ... 294.6495 
   2. filename: filename [character] rawdata/flu1.txt rawdata/flu2.txt ... rawdata/flu6.txt 
   3. c: c / (mg / l) [numeric] 0.05 0.10 ... 0.3 
[1] 1 3 5
[1] 1 2 3 4 5
[1] 1 2 3 4 5
[1] 3 4 5
[1] 1 2 3
 [1] 171 172 173 174 175 176 177 178 179 180 181
[1] 174 175 176 177 178 179 180 181
[1] 88 89 90 91 92 93 94
  [1] NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA
 [26] NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA
 [51] NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA
 [76] NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA
[101] NA
NULL
[1] 666 670 674 678

hyperSpec documentation built on May 2, 2019, 5:45 p.m.