Measuring AUC
Now that you've used cross-validation to compute average out-of-sample accuracy (after converting from an error), it's very easy to compute any other metric you might be interested in. All you have to do is pass it (or a list of metrics) in as an argument to the metrics parameter of xgb.cv(). 
Your job in this exercise is to compute another common metric used in binary classification - the area under the curve ("auc"). As before, churn_data is available in your workspace, along with the DMatrix churn_dmatrix and parameter dictionary params.
Este ejercicio forma parte del curso
Extreme Gradient Boosting with XGBoost
Instrucciones del ejercicio
- Perform 3-fold cross-validation with 
5boosting rounds and"auc"as your metric. - Print the 
"test-auc-mean"column ofcv_results. 
Ejercicio interactivo práctico
Prueba este ejercicio y completa el código de muestra.
# Perform cross_validation: cv_results
cv_results = ____(dtrain=____, params=____, 
                  nfold=____, num_boost_round=____, 
                  metrics="____", as_pandas=True, seed=123)
# Print cv_results
print(cv_results)
# Print the AUC
print((cv_results["____"]).iloc[-1])