[R] Accessing terminal datasets in Ctree()

[Achim Zeileis]

On Mon, 2 May 2016, Preetam Pal wrote:

> Hi guys,
>
> If I am applying ctree() on a data (specifying some control parameters like
> maxdepth), is there a way I can programmatically access the (smaller)
> datasets corresponding to the terminal nodes in the tree? Say, if there are
> 7 terminal nodes, I need those 7 datasets (of course, I can look at the
> respective node-splitting attributes and write out a filtering function -
> but clearly too much to ask for if I have a large number of terminal
> nodes). Intention is to perform regression on each of these terminal
> datasets.

If you use the "partykit" implementation you can do:

library("partykit")
ct <- ctree(Species ~ ., data = iris)
data_party(ct, id = 6)

to obtain the data associated with node 6 for example. You can also use 
ct[6] to obtain the subtree and ct[6]$data for its associated data.

For setting up a factor with the terminal node IDs, you can also use 
predict(ct, type = "node") and then use that in lm() etc.

Finally, note that there is also lmtree() and glmtree() for trees with 
(generalized) linear models in their nodes.

> Regards,
> Preetam
>
> -- 
> Preetam Pal
> (+91)-9432212774
> M-Stat 2nd Year,                                             Room No. N-114
> Statistics Division,                                           C.V.Raman
> Hall
> Indian Statistical Institute,                                 B.H.O.S.
> Kolkata.
>
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