ggdendro (version 0.1-20)

dendro_data.rpart: Extract data from classification tree object for plotting using ggplot.

Description

Extracts data to plot line segments and labels from a rpart classification tree object. This data can then be manipulated or plotted, e.g. using ggplot.

Usage

# S3 method for rpart
dendro_data(model, uniform = FALSE, branch = 1,
  compress = FALSE, nspace, minbranch = 0.3, ...)

Arguments

model

object of class "tree", e.g. the output of tree()

uniform

if TRUE, uniform vertical spacing of the nodes is used; this may be less cluttered when fitting a large plot onto a page. The default is to use a non-uniform spacing proportional to the error in the fit.

branch

controls the shape of the branches from parent to child node. Any number from 0 to 1 is allowed. A value of 1 gives square shouldered branches, a value of 0 give V shaped branches, with other values being intermediate.

compress

if FALSE, the leaf nodes will be at the horizontal plot coordinates of 1:nleaves. If TRUE, the routine attempts a more compact arrangement of the tree. The compaction algorithm assumes uniform=TRUE; surprisingly, the result is usually an improvement even when that is not the case.

nspace

the amount of extra space between a node with children and a leaf, as compared to the minimal space between leaves. Applies to compressed trees only. The default is the value of branch.

minbranch

set the minimum length for a branch to minbranch times the average branch length. This parameter is ignored if uniform=TRUE. Sometimes a split will give very little improvement, or even (in the classification case) no improvement at all. A tree with branch lengths strictly proportional to improvement leaves no room to squeeze in node labels.

...

ignored

Value

A list of three data frames:

segments

a data frame containing the line segment data

labels

a data frame containing the label text data

leaf_labels

a data frame containing the leaf label text data

Details

This code is in essence a copy of plot.rpart, retaining the plot data but without plotting toa plot device.

See Also

ggdendrogram

Other dendro_data methods: dendro_data.tree, dendro_data, dendrogram_data, rpart_labels

Other rpart functions: rpart_labels, rpart_segments

Examples

# NOT RUN {
### Demionstrate rpart

if(require(rpart)){
  require(ggplot2)
  fit <- rpart(Kyphosis ~ Age + Number + Start, method="class", data=kyphosis)
  fitr <- dendro_data(fit)
  ggplot() + 
    geom_segment(data=fitr$segments, aes(x=x, y=y, xend=xend, yend=yend)) + 
    geom_text(data=fitr$labels, aes(x=x, y=y, label=label)) +
    geom_text(data=fitr$leaf_labels, aes(x=x, y=y, label=label)) +
    theme_dendro()
}
# }