Im a currently working with ctree from R package "partykit" and I was wondering if there is a way to obtain the full path from terminal nodes to root. I would like to have for each leaf the full path to the root expressed as vectors containing the node ids.
library(partykit)
ct <- ctree(Species ~ ., data = iris)
Model formula:
Species ~ Sepal.Length + Sepal.Width + Petal.Length + Petal.Width
Fitted party:
[1] root
| [2] Petal.Length <= 1.9: setosa (n = 50, err = 0.0%)
| [3] Petal.Length > 1.9
| | [4] Petal.Width <= 1.7
| | | [5] Petal.Length <= 4.8: versicolor (n = 46, err = 2.2%)
| | | [6] Petal.Length > 4.8: versicolor (n = 8, err = 50.0%)
| | [7] Petal.Width > 1.7: virginica (n = 46, err = 2.2%)
Number of inner nodes: 3
Number of terminal nodes: 4
This is basically what I need:
[[1]]
[1] 2 1
[[2]]
[1] 5 4 3 1
[[3]]
[1] 6 4 3 1
[[4]]
[1] 7 3 1
I would appreciate any help! Thanks!
The following function should do the trick. The first line extracts a list of kids per node and from this you can recursively go through all nodes.
get_path <- function(object) {
## list of kids per node (NULL if terminal)
kids <- lapply(as.list(object$node), "[[", "kids")
## recursively add node IDs of children
add_ids <- function(x) {
ki <- kids[[x[1L]]]
if(is.null(ki)) {
return(list(x))
} else {
x <- lapply(ki, "c", x)
return(do.call("c", lapply(x, add_ids)))
}
}
add_ids(1L)
}
This can then be applied to any party
object:
get_path(ct)
## [[1]]
## [1] 2 1
##
## [[2]]
## [1] 5 4 3 1
##
## [[3]]
## [1] 6 4 3 1
##
## [[4]]
## [1] 7 3 1