Important features identified by PLS-DA and VIP scores.

A VIP score is a measure of a variable’s importance in the PLS-DA model. It summarizes the contribution a variable makes to the model. The VIP score of a variable is calculated as a weighted sum of the squared correlations between the PLS-DA components and the original variable. The weights correspond to the percentage variation explained by the PLS-DA component in the model. The number of terms in the sum depends on the number of PLS-DA components found to be significant in distinguishing the classes. The Y axis indicates the VIP scores corresponding to each variable on the X- axis. The red asterisks indicate the factors with the highest VIP scores and thus are the most contributory variables in class discrimination in the PLS-DA model.