Rough set based wavelength selection in near-infrared spectral analysis

• Rough set algorithm could provide reliable model variables for NIR analysis.
• Rough set could be applied to NIR band assignment.
• Fast determination of Phe by NIR is possible with further research.

Rough set based procedure was proposed as a new methodology to select component-specific wavelengths for near-infrared (NIR) spectral analysis. Information gain (IG) was employed to regulate the size of the discernibility matrix and decrease the memory requirements of rough set based reduction. This procedure involved submitting the resulting subsets of wavelengths to the analytical models in question. The utility of this method was illustrated by an analysis of classification models for phenylalanine (Phe) in plasma. The wavelength selection algorithm was compared with correlation based feature selection (CRFS) method and consistency based feature selection (CSFS) approach. Model fit was assessed using 10-fold cross-validation (10-fold CV) and leave-one out (LOO) approach. The predictability of the model was evaluated by an external prediction set. Furthermore, another two NIR data sets, obtained from the published literatures, were used to develop the quantitative models and validate the rough set based wavelength selection method. This study demonstrates conclusively that reducts of rough set could preserve the spectra–structure relationship and provide reliable model variables for NIR analysis. The results also indicate that rough set algorithm may hold promise for application as an additional feasible technique to NIR band assignment. As a fast, simple and noninvasive measurement, it is hopeful to find a clinical use in the diagnosis of unusual Phe elevation with further research.