osc: Orthogonal Signal Correction

In ChristianGoueguel/specProc: Preprocessing Tools For Laser-Induced Breakdown Spectroscopy (LIBS) Spectra

Orthogonal Signal Correction

Description

This function implements three orthogonal signal correction (OSC) algorithms, which are a class of preprocessing techniques designed to minimize, in a set of spectral data, the systematic variability or noise not directly related to or correlated with the response vector or property of interest.

Usage

osc(
  x,
  y,
  method = "sjoblom",
  center = TRUE,
  scale = FALSE,
  ncomp = 10,
  tol = 0.001,
  max.iter = 10
)

Arguments

x	A matrix or data frame of the predictor variables.
y	A vector of the response variable.
method	A character string indicating the OSC method to use. Accepted values are "wold", "sjoblom" and "fearn". Default is "sjoblom".
center	A logical value indicating whether to mean-centered x and y. Default is TRUE.
scale	A logical value indicating whether to scale x and y. Default is FALSE.
ncomp	An integer representing the number of components, which defines how many times the entire process will be performed. Default value is 10.
tol	A numeric value representing the tolerance for convergence. The default value is 1e-3.
max.iter	An integer representing the maximum number of iterations. The default value is 10.

Details

The OSC algorithm identifies and removes the orthogonal variation in the input spectral matrix, \textbf{X}, by iteratively deflating \textbf{X} with respect to the response vector \textbf{y}. The resulting \textbf{X}-matrix contains only the variation that is relevant to the \textbf{y}-vector, which can then be used for further modeling or analysis. This function implements three different methods for OSC: the original method proposed by Wold et al. (1998), the method proposed by Sjöblom et al. (1998), and the method proposed by Fearn (2000).

Value

An list containing the following components:

• correction: The corrected matrix.

• scores: The orthogonal scores matrix.

• loadings: The orthogonal loadings matrix.

• weights: The orthogonal weights matrix.

• R2: The value of the explained variance.

• angle: The value of the orthogonalization angle.

Author(s)

Christian L. Goueguel

References

• Sjöblom, J., Svensson, O., Josefson, M., Kullberg, H., Wold, S., (1998). An evaluation of orthogonal signal correction applied to calibration transfer of near infrared spectra. Chemometrics Intell. Lab. Syst., 44(1):229-244.

• Fearn, T., (2000). On orthogonal signal correction. Chemometrics Intell. Lab. Syst., 50(1):47-52.

• Wold, S., Antti, H., Lindgren, F., Ohman, J. (1998). Orthogonal signal correction of near-infrared spectra. Chemometrics Intell. Lab. Syst., 44(1):175-185.

• Svensson, O., Kourti, T. and MacGregor, J.F., (2002). An investigation of orthogonal correction algorithms and their characteristics. Journal of Chemometrics, 16(1):176-188.

ChristianGoueguel/specProc documentation built on Nov. 9, 2024, 3:23 p.m.