itree (version 0.1)

snip.itree: Snip Subtrees of an itree Object

Description

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

Usage

snip.itree(x, toss)

Arguments

x

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

Value

A itree 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).

Details

A dendrogram of itree 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 y-value, 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 itree object.

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

See Also

plot.itree

Examples

## dataset not in R
## same as rpart:
## Not run: 
# z.survey <- itree(market.survey) #grow the itree object
# plot(z.survey) #plot the tree
# z.survey2 <- snip.itree(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)
#works with itree fits as well:
z.auto <- itree(Mileage ~ Weight, method="purity",car.test.frame)
#snip off the long branch:
z.auto2 <- snip.itree(z.auto,toss=3)