[R] Random Forest
Liaw, Andy
andy_liaw at merck.com
Mon Mar 1 16:14:26 CET 2010
From: Dror
>
> Hi,
> I'm working with randomForest package and i have 2 questions:
> 1. how can i drop a specific tree from the forest?
Answered in another post.
> 2. i'm trying to get the voting of each tree in a prediction
> datum using the
> folowing code
> > pr<-predict(RF,NewData,type="prob",predict.all=TRUE)
> my forest has 300 trees and i get lower number of votes:
> > length(pr$individual)
> [1] 275
> > RF
> Call:
> randomForest(formula = RFformula, data = adult, ntree = 300,
> mtry = 1,
> keep.forest = TRUE)
> Type of random forest: classification
> Number of trees: 300
> No. of variables tried at each split: 1
> Am i doing something wrong? how can i know which of the 300
> trees didn't
> cast a vote?
Hope this example is clear:
R> iris.rf = randomForest(Species~., iris, ntree=148)
R> iris.p = predict(iris.rf, iris, predict.all=TRUE)
R> str(iris.p$individual)
chr [1:150, 1:148] "setosa" "setosa" "setosa" "setosa" "setosa" ...
- attr(*, "dimnames")=List of 2
..$ : chr [1:150] "1" "2" "3" "4" ...
..$ : NULL
R> length(iris.p$individual)
[1] 22200
Andy
> Thanks in advance
> Dror
> --
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