Abstract：In the analysis of near-infrared spectroscopy data, full-spectrum data has the characteristics of multiple wavelength points, large redundancy, and serious collinearity. This leads to some wavelength points that have no positive effect on the establishment of the correction model and even reduce the model’s predictive ability. Wavelength selection has proven to be an important method to avoid above problems effectively. Aiming at the characteristics of near-infrared spectroscopy, a wavelength selection algorithm based on the combination of Direct Orthogonal Signal Correction (DOSC) and Monte Carlo (MC) is proposed. Unlike most methods of selecting wavelength according to its “importance”, MC-DOSC selects wavelength according to its “unimportance”. The “unimportance” of wavelength is measured by the weight W of DOSC. Specifically, first, normalize was the probability of wavelength being filtered to establish the probability model of wavelength selection, and Monte Carlo random sampling is used to obtain the set of N wavelength subsets. The selected wavelength point is used to establish a PLS model in each sampling process, and the corresponding cross-validation root mean square error (RMSECV) is calculated. After N times of random sampling, the wavelength subset corresponding to the PLS model with minimum RMSECV is selected as the candidate subset. The spectral data contained in the candidate subset is used as a new spectral matrix, and the above process is repeated until the RMSECV no longer drops. After the iteration stops, the candidate subset with the smallest RMSECV is taken as the best wavelength subset. And compared with the three algorithms of Monte Carlo Uninformative Variable Elimination (MCUVE), Genetic Algorithm (GA) and Competitive Adaptive Weight Sampling (CARS). Experimental results show that the algorithm can greatly reduce the number of wavelength points, and the prediction ability of the corresponding PLS model is also improved. In the experimental results of the corn data set, the number of wavelength points is reduced from 700 in the full spectrum to 15. The correlation coefficient of the prediction set is increased from 0.828 2 to 0.931 4, and the RMSEP is reduced from 0.109 8 to 0.071 3. In the experimental results of the gasoline data set, the number of wavelength points was reduced from 301 in the full spectrum to 31. The correlation coefficient of the prediction set was increased from 0.987 5 to 0.993 9, and the RMSEP was reduced from 0.255 to 0.178 8. The performance of this algorithm in the two data sets is better than the three algorithms compared.
Key words：Near-infrared spectroscopy; Wavelength selection; Direct orthogonal signal correction; Monte Carlo; Partial least squares
谢林江，洪明坚，余志荣. 一种结合直接正交信号校正与蒙特卡罗的波长选择方法[J]. 光谱学与光谱分析, 2022, 42(02): 440-445.
XIE Lin-jiang, HONG Ming-jian, YU Zhi-rong. A Wavelength Selection Method Combining Direct Orthogonal Signal Correction and Monte Carlo. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2022, 42(02): 440-445.
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