Regression analysis was conducted using Matlab 2021b. The gaussian process regression model was used to predict the percentage fraction of fetuin within the fetuin/asialofetuin mixture. DAPC was first performed on the dataset for the wavenumber from 400-1650 cm - 1 , and then the resulting canonicals were used in regression analysis. A 5-fold crossvalidation was performed on the model to evaluate the regression performance. The model was evaluated based on the normalized mean square error (NMSE) and coefficient of determination (R 2 ). For the collective spectra regression, the dataset was built in the same way as described in the classification. Then the spectra went through the same regression algorithm and were evaluated based on the same performance metrics (NMSE and R 2 ).