Fig. 5

Tuning parameters when using grid-search method and cross validate. The RMSE was used to select the optimal model using the smallest value. a Artificial neural network model. The optimal ANN model used a medium degree of regularization (i.e., lambda = 0.01) and a single hidden layer with two hidden units. b Support vector machine model. When using the radial basis function, the SVM model was numerically optimal at sigma = 0.3592 and C = 2 on the log₂ scale. c Random forest model. The RF model was numerically optimal at mtry = 2