Question

I am using the party package in R.

I would like to get various statistics (mean, median, etc) from various nodes of the resultant tree, but I cannot see how to do this. For example

airq <- subset(airquality, !is.na(Ozone))
airct <- ctree(Ozone ~ ., data = airq, 
                   controls = ctree_control(maxsurrogate = 3))
airct
plot(airct)

results in a tree with 4 terminal nodes. How would I get the mean airquality for each of those nodes?

Answer 1

This is surprisingly harder than I thought. Try something like this:

a <- by(airq,where(airct),colMeans) #or whatever function you desire for colMeans
a
a$"3" #access at node three
a[["3"]] #same thing

You might find some other useful examples with ?`BinaryTree-class`.