Returns the area under the curve ("AUC") of a receiver-operating characteristic curve for the given predicted and actual values.
    
     
    auc(actual, pred)
    
    Arguments
    
    
    
      | actual | Logical vector: TRUEfor positive class. 
If not a logical vector, the result is interpreted as one if safe to do so,
 viz. ifactualcontains precisely two unique values and is either a numeric vector,
 an ordered factor, or the unique values areFALSEandTRUE(case-insensitively).
 Anything else is an error. | 
    
      | pred | Numeric (double) vector the same length as actualgiving the predicted probability ofTRUE. Must be a numeric vector the same length asactual. | 
    
    
    Source
    Source code based on Metrics::auc from Ben Hamner and Michael Frasco and Erin LeDell from the Metrics package.