How to extract tree structure from ctree function?

Question

I am trying to extract the tree information from the output of ctree. I tried the Class "BinaryTree" info but with no success. Any input is appreciated.

Thank You

• Dason: Are you talking about ctree found in the 'party' package?

Answer 1

The ctree objects are S4 objects at least at the top, and the tree information is in the "tree" slot. The "tree slot can be access ed with the @ operator. If you take the first example in the help(ctree) page you can get a graphical display with:

plot(airct)

enter image description here

And then you can look are branches of the tree by traversing with list operations. The "leaves" of the tree are descendents of nodes with "terminal"==TRUE:

> airct@tree$right$terminal
[1] FALSE
> airct@tree$left$terminal
[1] FALSE
> airct@tree$right$right$terminal
[1] TRUE
> airct@tree$right$left$terminal
[1] TRUE
> airct@tree$left$left$terminal
[1] TRUE
> airct@tree$left$right$terminal
[1] FALSE

Information at nodes above the leaves can also be recovered:

> airct@tree$left$right
4) Temp <= 77; criterion = 0.997, statistic = 11.599
 5)* weights = 48 
4) Temp > 77
 6)* weights = 21 

This is the same information that the nodes function will recover if you know the number of the node:

> nodes(airct,4)
[[1]]
4) Temp <= 77; criterion = 0.997, statistic = 11.599
 5)* weights = 48 
4) Temp > 77
 6)* weights = 21 

• Josh O'Brien: @user1122211 - To show that DWin answered your question -- quite nicely I'd say -- and as another form of thanks to him, you can 'accept' it by clicking the checkmark directly to its left. Thanks.

Answer 2

The mlmeta R package converts fitted ctree models to SAS code. It can be easily adapted to other languages and is generally instructive on the internals of the object.

Answer 3

Let's say your ctree model is named ct. Then

print(ct)

worked for me to see the tree structure.