proximetricsR (version 0.6.5)

prep_resample: Resampling constructor for spectral preprocessing

Description

Creates a preprocessing constructor for resampling spectral data to a new wavelength grid. The constructor is intended to be passed to preprocess_recipe and executed via process.

Usage

prep_resample(grid)

Value

An object of class preprocessing to be used in preprocess_recipe and executed by process.

Arguments

grid

Either a numeric vector of length 3 specifying the target wavelength grid as c(min_wav, max_wav, resolution), or the character string "proxiscout" to resample to the standard NeoSpectra wavenumber grid (see Details).

When grid is a numeric vector:

• grid[1] (min_wav): minimum wavelength of the target grid.

• grid[2] (max_wav): maximum wavelength; must be greater than min_wav.

• grid[3] (resolution): spacing between wavelengths; must be positive.

Extrapolation beyond the range of the input wavelengths is never allowed.

Author

Leonardo Ramirez-Lopez and Claudio Orellano

Details

User-defined grid (grid = c(min_wav, max_wav, resolution)): resamples spectra to the specified target grid using natural spline interpolation via resample. Column names of X must be coercible to numeric wavelength values. This mode is compatible with the "proximate" device.

NeoSpectra grid (grid = "proxiscout"): resamples spectra to the standard wavenumber grid of NeoSpectra NIR scanners (approx. 3921.569 to 7407.407 \(cm^{-1}\), ~256 channels at ~13.617 \(cm^{-1}\) steps). Only wavenumbers overlapping with the input range are retained. This mode is compatible with the "proxiscout" device.

See Also

preprocess_recipe, process, get_proxiscout_wavenumbers

Examples

data("NIRcannabis")
X <- NIRcannabis$spc

# User-defined grid (proximate)
rs <- prep_resample(grid = c(1001, 1700, 2))
recipe <- preprocess_recipe(rs, device = "proximate")
X_rs <- process(X, recipe)