Random Forest in R

Question

If x is a Random Forest in R, for example,

x <- cforest (y~ a+b+c, data = football),

what does x[[9]] mean?

Answer 1

You can't subset this object, so in some sense, x[[9]] is nothing, it is not accessible as such.

x is an object of S4 class "RandomForest-class" . This class is documented on help page ?'RandomForest-class' . The slots of this object are named and described there. You can also get the slot names via slotNames()

library("party")
foo <- cforest(ME ~ ., data = mammoexp, control = cforest_unbiased(ntree = 50))

> slotNames(foo)
 [1] "ensemble"            "where"               "weights"            
 [4] "initweights"         "data"                "responses"          
 [7] "cond_distr_response" "predict_response"    "prediction_weights" 
[10] "get_where"           "update"

If by x[[9]] you meant the 9th slot, then that is predict_weights and ?'RandomForest-class' tells us that this is

 ‘prediction_weights’: a function for extracting weights from
      terminal nodes.