xgobi (version 1.2-15)

quadplot: Tetrahedral Display for Four-Category Proportions using XGobi

Description

Four-category proportions are visualized as points inside a tetrahedron, using xgobi.

Usage

quadplot(mat4, pointlabs  = rownames(mat4), vertexlabs = paste(1:4), normalize  = median(abs(c(mat4))) > 1)

Arguments

mat4

matrix with 4 columns containing the data

pointlabs

character array of labels for rows of data; by default it is the row number as a string.

vertexlabs

character array of length 4 of labels for the vertices; by default it is the column number as a string.

normalize

logical variable indicating whether or not to force each row of data to have unit sum before display, default is false.

Details

The set of all four-category proportions, or, alternatively, probability measures on finite probability fields with 4 atomic events, is the set of nonnegative 4-vectors whose components sum up to 1. The function quadplot uses xgobi to represent such vectors graphically as points inside a tetrahetron with height 1: the four components of the vector are the distances of the point to each of the sides of the tetrahetron. Each vertex of the tetrahedron corresponds to the degenerate probability distribution in which one of the atomic events has probability 1 and the others have probability 0. The labels of these vertices indicate the event which has probability 1.

References

quadplot was posted by Jim Ramsay to S-news on Fri, 21 May 1993 14:03:15 EDT.

Examples

data(PaulKAI)
quadplot(PaulKAI, normalize = TRUE)