The predict method shows standardized probability?

Question

I'm using the AdaBoostClassifier in Scikit-learn and always get an average probability of 0.5 regardless of how unbalanced the training sets are. The class predictions (predict_) seems to give correct estimates, but these aren't reflected in the predict_probas method which always average to 0.5.

If my "real" probability is 0.02, how do I transform the standardized probability to reflect that proportion?

Answer 1

Do you mean you get probabilities per sample that are 1/n_classes on average? That's necessarily the case; the probabilities reported by predict_proba are the conditional class probability distribution P(y|X) over all values for y. To produce different probabilities, perform any necessary computations according to your probability model.