[R] Help me! using random Forest package, how to calculate Error Rates in the training set ?

[Liaw, Andy]

From: bbslover
> 
> now I am learining random forest and using random forest 
> package, I can get
> the OOB error rates, and test set rate, now I want to get the 
> training set
> error rate, how can I do?
> 
> pgp.rf<-randomForest(x.tr,y.tr,x.ts,y.ts,ntree=1e3,keep.forest
> =FALSE,do.trace=1e2)    
> using the code can get oob and test set error rate, if I 
> replace x.ts and
> y.ts with x.tr and y.tr,respectively,  is the error rate in 
> the training set
> ?   
> 
> pgp.rf<-randomForest(x.tr,y.tr,x.tr,y.tr,ntree=1e3,keep.forest
> =FALSE,do.trace=1e2) 
> 
> this time, I get oob error rates and training set error rate, 
> is  right?

Yes, or if you used keep.forest=TRUE, feed predict() with your x.tr and
compare that with y.tr.

However, I really don't understand why people compute "training error
rate": what useful information can you get from it?

Andy
 
> thank you!
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