vcd (version 1.3-2)

strucplot: Structured Displays of Contingency Tables

Description

This modular function visualizes certain aspects of high-dimensional contingency tables in a hierarchical way.

Usage

strucplot(x, residuals = NULL, expected = NULL,
  condvars = NULL, shade = NULL, type = c("observed", "expected"),
  residuals_type = NULL, df = NULL, split_vertical = NULL, 
  spacing = spacing_equal, spacing_args = list(),
  gp = NULL, gp_args = list(),
  labeling = labeling_border, labeling_args = list(),
  core = struc_mosaic, core_args = list(),
  legend = NULL, legend_args = list(),
  main = NULL, sub = NULL, margins = unit(3, "lines"),
  title_margins = NULL, legend_width = NULL,
  main_gp = gpar(fontsize = 20), sub_gp = gpar(fontsize = 15),
  newpage = TRUE, pop = TRUE, keep_aspect_ratio = NULL, prefix = "", ...)

Arguments

x

a contingency table in array form, with optional category labels specified in the dimnames attribute.

residuals

optionally, an array of residuals of the same dimension as x (see details).

expected

optionally, an array of expected values of the same dimension as x, or alternatively the corresponding independence model specification as used by loglin or

df

degrees of freedom passed to the shading functions used for inference. Will be calculated (and overwritten if specified) if both expected and residuals are NULL, or if expected is given a for

condvars

number of conditioning variables, if any; those are expected to be ordered first in the table. This information is used for computing the expected values, and is also passed to the spacing functions (see

shade

logical specifying whether gp should be used or not (see gp). If TRUE and expected is unspecified, a default model is fitted: if condvars is specified, a corresponding conditiona

residuals_type

a character string indicating the type of residuals to be computed when none are supplied. If residuals is NULL, residuals_type must be one of "pearson" (default; giving components of Pearson

type

a character string indicating whether the observed or the expected values of the table should be visualized.

split_vertical

vector of logicals of length $k$, where $k$ is the number of margins of x (values are recycled as needed). A TRUE component indicates that the tile(s) of the corresponding dimension should be split vertically, F

spacing

spacing object, spacing function, or a corresponding generating function (see details and spacings).

spacing_args

list of arguments for the spacing-generating function, if specified.

gp

object of class "gpar", shading function or a corresponding generating function (see details and shadings). Components of "gpar" objects are recycled as needed along t

gp_args

list of arguments for the shading-generating function, if specified.

labeling

either a logical, or a labeling function, or a corresponding generating function (see details and labelings. If FALSE or NULL, no labeling is produced.

labeling_args

list of arguments for the labeling-generating function, if specified.

core

either a core function, or a corresponding generating function (see details). Currently, generating functions for mosaic plots (struc_mosaic), association plots (

core_args

list of arguments for the core-generating function, if specified.

legend

either a legend-generating function, or a legend function (see details and legends), or a logical. If legend is NULL or TRUE and gp is a funct

legend_args

list of arguments for the legend-generating function, if specified.

main

either a logical, or a character string used for plotting the main title. If main is a logical and TRUE, the name of the object supplied as x is used.

sub

a character string used for plotting the subtitle. If sub is a logical and TRUE and main is unspecified, the name of the object supplied as x is used.

margins

either an object of class "unit" of length 4, or a numeric vector of length 4. The elements are recycled as needed. The four components specify the top, right, bottom, and left margin of the plot, respectively. When a numeric

title_margins

either an object of class "unit" of length 2, or a numeric vector of length 2. The elements are recycled as needed. The two components specify the top and bottom title margin of the plot, respectively. The default for eac

legend_width

An object of class "unit" of length 1 specifying the width of the legend (if any). Default: 5 lines.

pop

logical indicating whether the generated viewport tree should be removed at the end of the drawing or not.

main_gp, sub_gp

object of class "gpar" containing the graphical parameters used for the main (sub) title, if specified.

newpage

logical indicating whether a new page should be created for the plot or not.

keep_aspect_ratio

logical indicating whether the aspect ratio should be fixed or not. If unspecified, the default is TRUE for two-dimensional tables and FALSE otherwise.

prefix

optional character string used as a prefix for the generated viewport and grob names.

...

For convenience, list of arguments passed to the labeling-generating function used.

Value

• Invisibly, an object of class "structable" corresponding to the plot.

Details

This function---usually called by higher-level functions such as assoc and mosaic---generates conditioning plots of contingency tables. First, it sets up a set of viewports for main- and subtitles, legend, and the actual plot region. Then, residuals are computed as needed from observed and expected frequencies, where the expected frequencies are optionally computed for a specified independence model. Finally, the specified functions for spacing, gp, main plot, legend, and labeling are called to produce the plot. The function invisibly returns the "structable" object visualized.

Most elements of the plot, such as the core function, the spacing between the tiles, the shading of the tiles, the labeling, and the legend, are modularized in graphical appearance control (``grapcon'') functions and specified as parameters. For each element foo (= spacing, labeling, core, or legend), strucplot takes two arguments: foo and foo_args, which can be used to specify the parameters in the following alternative ways:

1. Passing a suitable function tofoowhich subsequently will be called fromstrucplotto compute shadings, labelings, etc.
2. Passing a correspondinggeneratingfunction tofoo, along with parameters passed tofoo_args, that generates such a function. Generating functions must inherit from classes"grapcon_generator"and"foo".
3. Except for the shading functions (shading_bar), passingfoo(foo_args)to thefooargument.
4. For shadings and spacings, passing the final parameter object itself; see the corresponding help pages for more details on the data structures.

If legends are drawn, a cinemascope-like layout is used for the plot to preserve the 1:1 aspect ratio.

If type = "expected", the expected values are passed to the observed argument of the core function, and the observed values to the expected argument.

Although the gp argument is typically used for shading, it can be used for arbitrary modifications of the tiles' graphics parameters (e.g., for highlighting particular cells, etc.).

References

Meyer D., Zeileis A., and Hornik K. (2006), The strucplot framework: Visualizing multi-way contingency tables with vcd. Journal of Statistical Software, 17(3), 1-48. URL http://www.jstatsoft.org/v17/i03/ and available as vignette("strucplot").

See Also

assoc, mosaic, sieve, struc_assoc, struc_sieve, struc_mosaic, structable, doubledecker, labelings, shadings, legends, spacings

Examples

data("Titanic")

strucplot(Titanic)
strucplot(Titanic, core = struc_assoc)
strucplot(Titanic, spacing = spacing_increase,
                   spacing_args = list(start = 0.5, rate = 1.5))
strucplot(Titanic, spacing = spacing_increase(start = 0.5, rate = 1.5))

## modify a tile's color
strucplot(Titanic, pop = FALSE)
grid.edit("rect:Class=1st,Sex=Male,Age=Adult,Survived=Yes",
          gp = gpar(fill = "red"))