I have two classifiers which try to classify the same data sets. In order to check the efficiency of the classifiers I intend to plot the curves and calculate the AUC value. The concern is that one of the classifiers always produce positive values as the scores (actually it is the p value) but the other classifier produces both positive and negative values as the scores(it has its own producing score method rather than producing pvalues). Should I take the absolute values for the second scores when plotting the roc curves and calculating the AUC or I can use scores as they are (both positive and negative). When I make the absolute values for the second classifier to plot the curves the AUC amount decreases.
Thank you in advance.