An S4 class that extends ROCR::performance-class to hold
the results of multiple model evaluations.
Slots
performance
list of ROCR performance objects. Each object is
calculated for the corresponding ROCR prediction object held in the
PredictionList object supplied to the constructor function
auc
numeric vector containing the area under the curve for each
performance object
categories
numeric vector of land use categories for which performance
objects were created
labels
character vector with labels corresponding to categories
providing 
.