path.rpart               package:rpart               R Documentation

Follow Paths to Selected Nodes of an Rpart Object

Description:

     Returns a names list where each element contains the splits on the
     path from the root to the selected nodes.

Usage:

     path.rpart(tree, nodes, pretty=0, print.it=TRUE)

Arguments:

    tree: fitted model object of class 'rpart'.  This is assumed to be
          the result of some function that produces an object with the
          same named components as that returned by the 'rpart'
          function. 

   nodes: an integer vector containing indices (node numbers) of all
          nodes for which paths are desired.  If missing, user selects
          nodes as described below.  

  pretty: an integer denoting the extent to which factor levels in
          split labels will be abbreviated.  A value of (0) signifies
          no abbreviation.  A 'NULL', the default, signifies using
          elements of letters to represent the different factor levels. 

print.it: Logical. Denotes whether paths will be printed out as nodes
          are interactively selected.   Irrelevant if 'nodes' argument
          is supplied. 

Details:

     The function has a required argument as an 'rpart' object  and a
     list of nodes as optional arguments.  Omitting a list of nodes
     will cause the function to  wait  for  the  user  to select  nodes
      from the dendogram.  It will return a list, with one component
     for each node  specified  or  selected. The  component  contains
     the sequence of splits leading to that node.  In the graphical 
     interation,  the  individual paths are printed out as nodes are
     selected.

Value:

     A named (by node) list, each element of which contains all the 
     splits  on the path from the root to the specified or selected
     nodes.

Graphical Interaction:

     A dendrogram of the 'rpart' object is expected to be visible  on
     the graphics  device, and a graphics input device (eg a mouse) is
     required.  Clicking (the selection button)  on  a  node selects 
     that  node.   This  process  may  be repeated any number of times.
      Clicking the exit button will  stop  the selection process and
     return the list of paths.

References:

     This function was modified from 'path.tree' in S.

See Also:

     'rpart'

Examples:

     data(kyphosis)
     fit <- rpart(Kyphosis ~ Age + Number + Start, data=kyphosis)
     summary(fit)
     path.rpart(fit, node=c(11, 22))

