of-fit measure to be calculated. Options are <code>"cor"</code> (correlation between observed and predicted values), <code>"scor"</code> (Spearman correlation between observed and predicted values), <code>"RMSE"</code> (root mean squared error of prediction), <code>"MAE"</code> (Mean Absolute Error), <code>"MARNE"</code> (Mean Absolute Range Normalized Error), <code>"TjurR2"</code> (Tjur's R2 measure, only for binary data), <code>"R2"</code> (R-squared as the square of the correlation) and <code>"sR2"</code