After ctree builds a tree, how would I determine the direction missing values
follow by examining the BinaryTree-class object? For instance in the example
below Bare.nuclei has 16 missing values and is used for the first split, but
the missing values are not listed in either set of factors. (I have the same
question for missing values among numeric [non-factor] values, but I assume the
answer is similar.)
> require(party)
> require(mlbench)
> data(BreastCancer)
> BreastCancer$Id <- NULL
> ct <- ctree(Class ~ . , data=BreastCancer, controls = ctree_control(maxdepth
> = 1))
> ct
Conditional inference tree with 2 terminal nodes
Response: Class
Inputs: Cl.thickness, Cell.size, Cell.shape, Marg.adhesion, Epith.c.size,
Bare.nuclei, Bl.cromatin, Normal.nucleoli, Mitoses
Number of observations: 699
1) Bare.nuclei == {1, 2}; criterion = 1, statistic = 488.294
2)* weights = 448
1) Bare.nuclei == {3, 4, 5, 6, 7, 8, 9, 10}
3)* weights = 251
> sum(is.na(BreastCancer$Bare.nuclei))
[1] 16
> nodes(ct, 1)[[1]]$psplit
Bare.nuclei == {1, 2}
> nodes(ct, 1)[[1]]$ssplit
list()
Based on below, the answer is node 2, but I don't see it in the object.
> sum(BreastCancer$Bare.nuclei %in% c(1,2,NA))
[1] 448
> sum(BreastCancer$Bare.nuclei %in% c(1,2))
[1] 432
> sum(BreastCancer$Bare.nuclei %in% c(3:10))
[1] 251
Andrew
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