# R: Snip Subtrees of an Rpart Object

snip.rpart {rpart} | R Documentation

## Snip Subtrees of an Rpart Object

### Description

Creates a "snipped" rpart object, containing the nodes that remain after selected subtrees have been snipped off. The user can snip nodes using the toss arguement, or interactively by clicking the mouse button on specified nodes within the graphics window.

### Usage

    snip.rpart(x, toss)

### Arguments

`x` | 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.
`toss` | an integer vector containing indices (node numbers) of all subtrees to be snipped off. If missing, user selects branches to snip off as described below.

### Details

A dendrogram of `rpart` is expected to be visible on the graphics device, and a graphics input device (e.g., a mouse) is required. Clicking (the selection button) on a node displays the node number, sample size, response yvalue, and Error (dev). Clicking a second time on the same node snips that subtree off and visually erases the subtree. This process may be repeated an number of times. Warnings result from selecting the root or leaf nodes. Clicking the exit button will stop the snipping process and return the resulting `rpart` object.

See the documentation for the specific graphics device for details on graphical input techniques.

### Value

a `rpart` object containing the nodes that remain after specified or selected subtrees have been snipped off.

### Warning

Visually erasing the plot is done by over-plotting with the background colour. This will do nothing if the background is transparent (often true for screen devices).

### See Also

`plot.rpart`

### Examples

    ## dataset not in R
    ## Not run:
    z.survey <- rpart(market.survey) #grow the rpart object
    plot(z.survey) #plot the tree
    z.survey2 <- snip.rpart(z.survey,toss=2) #trim subtree at node 2
    plot(z.survey2) #plot new tree

    # can also interactively select the node using the mouse in the
    # graphics window
    ## End(Not run)

[Package rpart version 3.1-37 Index]