party (version 0.2-3)

Panel Generating Functions: Visualization of Binary Regression Trees

Description

The plot method for BinaryTree objects is rather flexible and can be extended by panel functions. Some pre-defined panel generating functions for the most important cases are documented here.

Usage

node_inner(ctreeobj, digits = 3, abbreviate = FALSE, 
  fill = "white", id = TRUE)
node_terminal(ctreeobj, digits = 3, abbreviate = FALSE, 
  fill = c("lightgray", "white"), id = TRUE)
edge_simple(ctreeobj, digits = 3, abbreviate = FALSE)
node_surv(ctreeobj, ylines = 2, id = TRUE, ...)
node_barplot(ctreeobj, col = "black", fill = "lightgray", ymax = NULL,
  ylines = 3, widths = 1, gap = NULL, id = TRUE)
node_boxplot(ctreeobj, col = "black", fill = "lightgray",  width = 0.5,
  yscale = NULL, ylines = 3, id = TRUE)
node_hist(ctreeobj, col = "black", fill = "lightgray", freq = FALSE,
  horizontal = TRUE, xscale = NULL, ymax = NULL, ylines = 3,
  id = TRUE, ...)
node_density(ctreeobj, col = "black", rug = TRUE, horizontal = TRUE,
  xscale = NULL, yscale = NULL, ylines = 3, id = TRUE)

Arguments

ctreeobj

an object of class BinaryTree.

digits

integer, used for formating numbers.

abbreviate

logical indicating whether strings should be abbreviated.

col

a color for points and lines.

fill

a color to filling rectangles.

id

a logical indicating whether the node ID should be plotted.

ylines

number of lines in y-direction.

widths

widths in barplots.

width

width in boxplots.

gap

gap between bars in a barplot (node_barplot).

yscale

limits in y-direction

xscale

limits in x-direction

ymax

upper limit in y-direction

horizontal

logical indicating if the plots should be horizontal.

freq

logical; if TRUE, the histogram graphic is a representation of frequencies. If FALSE, probabilities are plotted.

rug

logical indicating if a rug representation should be added.

...

additional arguments passed to callies.

Details

The plot method for BinaryTree objects provides an extensible framework for the visualization of binary regression trees. The user is allowed to specify panel functions for plotting terminal and inner nodes as well as the corresponding edges. For convenience, the panel generating functions node_inner and edge_simple return panel functions to draw inner nodes and left and right edges. For drawing terminal nodes, the functions returned by the other panel functions can be used. The panel generating function panel_terminal_node is a terse text-based representation of terminal nodes.

Graphical representations of terminal nodes are available and depend on the measurement scale of the response variable the tree was fitted to. node_surv returns a functions that plots Kaplan-Meier curves in each terminal node. node_barplot, node_boxplot, node_hist and node_density can be used to plot barplots, boxplots, histograms and estimated densities into the terminal nodes.

Examples

data(airquality)
  airq <- subset(airquality, !is.na(Ozone))
  airct <- ctree(Ozone ~ ., data = airq)

  ### very simple; the mean is given in each terminal node
  plot(airct, type = "simple")

  ### density estimates
  plot(airct, terminal_panel = node_density)
    
  ### histograms 
  plot(airct, terminal_panel = node_hist)

  ### boxplots
  plot(airct, terminal_panel = node_boxplot, drop_terminal = TRUE)

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