agreementplot.default {vcd}R Documentation

Bangdiwala's Observer Agreement Chart

Description

Representation of a k x k confusion matrix, where the observed and expected diagonal elements are represented by superposed black and white rectangles, respectively. The function also computes a statistic measuring the strength of agreement (relation of respective area sums).

Usage

## Default S3 method:
agreementplot(x, reverse.y = TRUE, main = "Agreement Chart",
              weights = c(1, 1 - 1/(ncol(x) - 1)^2), cex.main = 2, cex.lab = 1.5,
              xlab = names(dimnames(x))[2], ylab = names(dimnames(x))[1], ...)
## S3 method for class 'formula':
agreementplot(formula, data = NULL, ..., subset)

Arguments

x a confusion matrix, i.e. a table with equal-sized dimensions.
reverse.y if TRUE, the y axis is reversed (i.e., the rectangles' positions correspond to the contingency table).
main user-specified main title.
weights vector of weights for successive larger observed areas, used in the agreement strength statistic, and also for the shading. The first element should be 1.
cex.main font size of title.
cex.lab font size of labels.
xlab, ylab labels of x- and y-axis.
formula a formula, such as y ~ x. For details, see xtabs.
data a data.frame (or list), or a contingency table from which the variables in `formula' should be taken.
subset an optional vector specifying a subset of observations to be used for plotting.
... further graphics parameters (see par).

Details

Weights can be specified to allow for partial agreement, taking into account contributions from off-diagonal cells. A weight vector of length 1 means strict agreement only, each additional element increases the maximum number of disagreement steps.

Value

Invisibly returned, a list with components

Bangdiwala the unweighted agreement strength statistic
Bangdiwala.Weighted the weighted statistic
weights the weigtht vector used.

Author(s)

David Meyer
david.meyer@ci.tuwien.ac.at

References

Michael Friendly (2000), Visualizing Categorical Data. SAS Institute, Cary, NC.

Examples

data(SexualFun)
agreementplot(t(SexualFun))

data(MSPatients)
## Enlarge plot manually or use sth. like: X11(width = 12)!
par(mfrow = c(1,2))
agreementplot(t(MSPatients[,,1]), main = "Winnipeg Patients")
agreementplot(t(MSPatients[,,2]), main = "New Orleans Patients")
par(mfrow = c(1,1))

[Package vcd version 0.1-3.5 Index]