Wavelength trimming constructor for spectral preprocessing

Creates a preprocessing constructor for trimming spectral data to a specified wavelength band. The constructor is intended to be passed to preprocess_recipe and executed via process.

Usage

prep_wav_trim(
  band,
  trim_constant_edges = FALSE
)

Arguments

band: A numeric vector of length 2 giving the minimum and maximum wavenumber/wavelength to retain. Columns of X outside this range are dropped. Pass c() (empty vector) to skip band trimming and only apply trim_constant_edges.
trim_constant_edges: A logical. If TRUE, constant or zero-valued columns at the left and right edges are removed after band trimming. Default is FALSE.

Value

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

Details

Band trimming retains only those columns whose names (coerced to numeric) fall within [min(band), max(band)]. If no columns fall within the band the original matrix is returned with a warning.

Constant edge trimming scans inward from each edge and drops columns that are identical to their immediate neighbour or are all zero. If trimming would leave fewer than two columns the step is skipped with a warning.

Author

Claudio Orellano and Leonardo Ramirez-Lopez

Examples

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

tr <- prep_wav_trim(band = c(1000, 1800))
recipe <- preprocess_recipe(tr, device = "proxiscout")
X_trim <- process(X, recipe)