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Fitting method constructors

Source: R/fit_constructors.R
fit_constructors.Rd

These functions create configuration objects that specify the regression method to be used within calibrate.

Usage

fit_plsr(ncomp, type = c("nwp", "standard", "modified"))

fit_xlsr(ncomp, type = c("nwp", "standard", "modified"), min_w = 3, max_w = 15)

Arguments

ncomp

a positive integer indicating the maximum number of PLS components to use.

type

a character string indicating the algorithm variant. One of "nwp" (default), "standard", or "modified".

  • "nwp": replicates the NIRWise PLUS method, which uses correlation-based weights with an additional slope correction applied to the weights and scores.

  • "standard": standard PLS using standardised covariances between spectra and reference values as weights.

  • "modified": modified PLS using correlations between spectra and reference values as weights.

min_w

a positive integer indicating the minimum window size for the XLS algorithm. Default is 3.

max_w

a positive integer indicating the maximum window size for the XLS algorithm. Must be greater than min_w. Default is 15.

Value

An object of class c("fit_plsr", "fit_constructor") or c("fit_xlsr", "fit_constructor") containing the specified parameters, to be passed to calibrate.

Details

There are two regression methods available:

Partial least squares (fit_plsr)

Uses PLS regression. The only parameter optimised is the number of components (ncomp). Three algorithm variants are available via type: "nwp", "standard", and "modified".

Extended partial least squares (fit_xlsr)

Uses the XLS algorithm. In addition to ncomp and type, the window range (min_w, max_w) controls the local smoothing applied within the algorithm.

See also

calibrate, calibrate_models

Author

Leonardo Ramirez-Lopez and Claudio Orellano

Examples

# PLS as in NIRWise PLUS
fit_plsr(ncomp = 15)
#> Fitting method: fit_plsr
#>   ncomp: 15 
#>   type : nwp 

# Standard PLS with 15 components
fit_plsr(ncomp = 15, type = "standard")
#> Fitting method: fit_plsr
#>   ncomp: 15 
#>   type : standard 

# Modified PLS with 15 components
fit_plsr(ncomp = 15, type = "modified")
#> Fitting method: fit_plsr
#>   ncomp: 15 
#>   type : modified 

# XLS as in NIRWise PLUS
fit_xlsr(ncomp = 10)
#> Fitting method: fit_xlsr
#>   ncomp: 10 
#>   type : nwp 
#>   min_w: 3 
#>   max_w: 15 

# Standard XLS with custom window range
fit_xlsr(ncomp = 10, type = "standard", min_w = 5, max_w = 20)
#> Fitting method: fit_xlsr
#>   ncomp: 10 
#>   type : standard 
#>   min_w: 5 
#>   max_w: 20