Figure 2

Receiver operating characteristic (ROC) plots of the models, which achieved the maximal F1 scores. The ROC plots shown belong to the models, which achieved the maximal F1 scores (table 2) in the five-fold cross-validation with either a removal (a) or replacement (b) preprocessing applied before the calculation of term weights. The ROC curves are vertical averaged (fixed false positive rates and averages of the corresponding true positive rates of each turn of the five-fold cross validation). In spite of decreasing standard deviation for larger numbers of available training sentences, the largest area under the curve (AUC) is achieved by classifiers for the category therapeutic application, which has least annotated sentences in the test/training corpus. See table 2 for the corresponding scalar AUC values of each plot.