Wild guess :
You need to have some kind of score for ROC to work (so you can work with a threshold), so a predict() that only returns classlabels probably won't work.

On 13.07.2012, at 15:25, blerta wrote:

> Hi, 
> 
> I don't really understand how ROCR works.  Here's another example with a
> randomforest model: I have the training dataset(bank_training) and testing
> dataset(bank_testing) and I ran a randomForest as below:
> 
>    bankrf<-randomForest(y~., bank_training, mtry=4, ntree=2,  
>    keep.forest=TRUE,importance=TRUE)         
>    bankrf.pred<-predict(bankrf, bank_testing)
>    library(ROCR)
>    pred<-prediction(bankrf.pred$y, bank_testing$y)
> 
> Here I get the error that the prediction format is incorrect? Where is the
> mistake?
> 
> Thanks in advance
> 
> --
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