@INDIRAR5552 

AUC is a standard metric in computer science and is calculated from the ROC curve. See e.g. https://en.wikipedia.org/wiki/Receiver_operating_characteristic.

Most ROC/AUC algorithms that you see use N datapoints with a propensity and a label. Since we don't have the N datapoints but only the aggregated bins for both the classifier and the predictors we calculate the AUC from these bins. Each bin represents #pos true positives with a propensity of #pos/(#pos + #neg) and #neg true negatives for which it gives that same propensity. 

Hope that helps.