# quadplot

##### Tetrahedral Display for Four-Category Proportions using XGobi

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 ramsay@psych.mcgill.ca
to S-news on Fri, 21 May 1993 14:03:15 EDT.

##### Examples

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

*Documentation reproduced from package xgobi, version 1.2-15, License: file LICENSE*