Fig. 2

Flowchart of the recursive feature elimination (RFE) with an Extreme Gradient Boosting (XGBoost) model as the estimator (XGBoost-RFE). The four curves in the figure represent the performance of the XGBoost-RFE model in 3-fold cross-validation and its mean performance. Based on the blue curve, the accuracy peaked when 4 or 5 features were retained.