Preprocessing Tools for Laser-Induced Breakdown Spectroscopy
Tools for exploring, preprocessing and modeling spectroscopic
data, developed for laser-induced breakdown spectroscopy (LIBS) and also
applicable to other techniques such as Raman, infrared, and inductively
coupled plasma optical emission spectroscopy. Covers the workflow from
raw spectra to calibrated results: peak finding and fitting, wavelength
calibration, baseline correction, normalization and scaling, orthogonal
signal correction including orthogonal partial least squares (OPLS;
Trygg and Wold (2002) ), calibration transfer,
calibration curves and figures of merit, and plasma diagnostics
(Boltzmann and Saha-Boltzmann plots, Stark broadening). Includes robust
tools for outlier detection and exploration: robust principal component
analysis (Hubert, Rousseeuw and Vanden Branden (2005)
), detection of deviating cells
(Rousseeuw and Van den Bossche (2018)
), PCA with cellwise outliers and
missing values (MacroPCA; Hubert, Rousseeuw and Van den Bossche (2019)
), robust transformations to central
normality (Raymaekers and Rousseeuw (2021)
), and self-organizing maps (Kohonen
(1982) ). Preprocessing steps are also available
as 'recipes' steps for 'tidymodels' workflows. Computationally intensive
steps are implemented in 'C++' via 'Rcpp' and 'RcppEigen'.