How to extract the splitting rules for the terminal nodes of ctree()

Question

I have a data set with 6 categorical variables with levels ranging from 5 to 28. I have obtained an output from ctree() (party package) with 17 terminal nodes. I have followed the inputs by @Galled from ctree() - How to get the list of splitting conditions for each terminal node? to arrive at my desired output.

But, I'm getting the following error post running the code:

Error in data.frame(ResulTable, Means, Counts) : 
  arguments imply differing number of rows: 17, 2

I have tried adding this extra lines:

ResulTable <- rbind(ResulTable, cbind(Node = Node, Path = Path2))

ResulTable$Node <- rownames(ResulTable)

melt(ResulTable)

but no success so far. Any pointers on where it is going wrong?

Answer 1

I would recommend to use the new partykit implementation of ctree() rather than the old party package, then you can use the function .list.rules.party(). This is not officially exported, yet, but can be leveraged to extract the desired information.

library("partykit")
airq <- subset(airquality, !is.na(Ozone))
ct <- ctree(Ozone ~ ., data = airq)
partykit:::.list.rules.party(ct)
##                                      3                                      5 
##             "Temp <= 82 & Wind <= 6.9" "Temp <= 82 & Wind > 6.9 & Temp <= 77" 
##                                      6                                      8 
##  "Temp <= 82 & Wind > 6.9 & Temp > 77"             "Temp > 82 & Wind <= 10.3" 
##                                      9 
##              "Temp > 82 & Wind > 10.3"