Difference between XGBRegressor and XGBClassifier

Question

I'm trying to understand the difference between xgboost.XGBRegressor and xgboost.sklearn.XGBClassifier.

Can someone explain the difference in a concise manner?

Because when I fit both classifiers with the exact same data, I get pretty different performance.

This is how I fit the data.

clf = xgboost.XGBRegressor(alpha=c)
#clf = xgboost.sklearn.XGBClassifier(alpha=c)

clf.fit(X_train, y_train)
y_pred = clf.predict(X_test)
print('Model roc auc score: %0.3f' % roc_auc_score(y_test, y_pred, average='macro', sample_weight=None))
print('Model pr auc score: %0.3f' % average_precision_score(y_test, y_pred))

when clf = xgboost.sklearn.XGBClassifier(alpha=c)

Model roc auc score: 0.544

Model pr auc score: 0.303

when clf = xgboost.XGBRegressor(alpha=c)

Model roc auc score: 0.703

Model pr auc score: 0.453

What would cause this performance difference?

Answer 1

XGBRegressor is for continuous target/outcome variables. These are often called "regression problems."

XGBClassifier is for categorical target/outcome variables. These are often called "classification problems."