R: Map spectra to new wavelength values.

interpolate_wl {photobiology} | R Documentation

## Map spectra to new wavelength values.

### Description

This function returns the result of interpolating spectral data from the original set of wavelengths to a new one.

### Usage

    interpolate_wl(x, w.length.out, fill, length.out, ...)

    ## Default S3 method:
    interpolate_wl(x, w.length.out, fill, length.out, ...)

    ## S3 method for class 'generic_spct'
    interpolate_wl(x, w.length.out = NULL, fill = NA,
      length.out = NULL, ...)

    ## S3 method for class 'generic_mspct'
    interpolate_wl(x, w.length.out = NULL, fill = NA,
      length.out = NULL, ..., .parallel = FALSE, .paropts = NULL)

### Arguments

`x` | an R object
`w.length.out` | numeric vector of wavelengths (nm)
`fill` | a value to be assigned to out of range wavelengths
`length.out` | numeric value
`...` | not used
`.parallel` | if TRUE, apply function in parallel, using parallel backend provided by foreach
`.paropts` | a list of additional options passed into the foreach function when parallel computation is enabled. This is important if (for example) your code relies on external data or packages: use the .export and .packages arguments to supply them so that all cluster nodes have the correct environment set up for computing.

### Details

If `length.out` it is a numeric value, then gives the number of rows in the output, if it is `NULL`, the values in the numeric vector `w.length.out` are used. If both are not `NULL` then the range of `w.length.out` and `length.out` are used to generate a vector of wavelength. A value of `NULL` for `fill` prevents extrapolation.

### Value

A new spectral object of the same class as argument `spct`.

### Methods (by class)

- `default`: Default for generic function

- `generic_spct`: Interpolate wavelength in an object of class "generic_spct" or derived.

- `generic_mspct`: Interpolate wavelength in an object of class "generic_mspct" or derived.

### Note

The default `fill = NA` fills extrapolated values with NA. Giving NULL as argument for `fill` deletes wavelengths outside the input data range from the returned spectrum. A numerical value can be also be provided as fill. This function calls `interpolate_spectrum` for each non-wavelength column in the input spectra object.

### Examples

    interpolate_wl(sun.spct, 400:500, NA)
    interpolate_wl(sun.spct, 400:500, NULL)
    interpolate_wl(sun.spct, seq(200, 1000, by=0.1), 0)
    interpolate_wl(sun.spct, c(400,500), length.out=201)

[Package photobiology version 0.9.21 Index]