nodeapply: Apply Functions Over Nodes

In partykit: A Toolkit for Recursive Partytioning

Apply Functions Over Nodes

Description

Returns a list of values obtained by applying a function to party or partynode objects.

Usage

nodeapply(obj, ids = 1, FUN = NULL, ...)
## S3 method for class 'partynode'
nodeapply(obj, ids = 1, FUN = NULL, ...)
## S3 method for class 'party'
nodeapply(obj, ids = 1, FUN = NULL, by_node = TRUE, ...)

Arguments

obj	an object of class partynode or party.
ids	integer vector of node identifiers to apply over.
FUN	a function to be applied to nodes. By default, the node itself is returned.
by_node	a logical indicating if FUN is applied to subsets of party objects or partynode objects (default).
...	additional arguments.

Details

Function FUN is applied to all nodes with node identifiers in ids for a partynode object. The method for party by default calls the nodeapply method on it's node slot. If by_node is FALSE, it is applied to a party object with root node ids.

Value

A list of results of length length(ids).

Examples

    ## a tree as flat list structure
    nodelist <- list(
        # root node
        list(id = 1L, split = partysplit(varid = 4L, breaks = 1.9),
            kids = 2:3),
        # V4 <= 1.9, terminal node
        list(id = 2L, info = "terminal A"),
        # V4 > 1.9
        list(id = 3L, split = partysplit(varid = 5L, breaks = 1.7),
            kids = c(4L, 7L)),
        # V5 <= 1.7
        list(id = 4L, split = partysplit(varid = 4L, breaks = 4.8),
            kids = 5:6),
        # V4 <= 4.8, terminal node
        list(id = 5L, info = "terminal B"),
        # V4 > 4.8, terminal node
        list(id = 6L, info = "terminal C"),
        # V5 > 1.7, terminal node
        list(id = 7L, info = "terminal D")
    )

    ## convert to a recursive structure
    node <- as.partynode(nodelist)

    ## return root node 
    nodeapply(node)

    ## return info slots of terminal nodes
    nodeapply(node, ids = nodeids(node, terminal = TRUE), 
        FUN = function(x) info_node(x))

    ## fit tree using rpart
    library("rpart")
    rp <- rpart(Kyphosis ~ Age + Number + Start, data = kyphosis)

    ## coerce to `constparty'
    rpk <- as.party(rp)

    ## extract nodeids
    nodeids(rpk)
    unlist(nodeapply(node_party(rpk), ids = nodeids(rpk), 
        FUN = id_node))
    unlist(nodeapply(rpk, ids = nodeids(rpk), FUN = id_node))

    ## but root nodes of party objects always have id = 1
    unlist(nodeapply(rpk, ids = nodeids(rpk), FUN = function(x) 
        id_node(node_party(x)), by_node = FALSE))

partykit documentation built on Sept. 11, 2024, 6:32 p.m.