biplot {mva} | R Documentation

## Biplot of Multivariate Data

### Description

Plot a biplot on the current graphics device.

### Usage

    biplot(x, ...)

    biplot.default(x, y, var.axes = TRUE, col, cex = rep(par("cex"), 2),
                   xlabs = NULL, ylabs = NULL, expand = 1,
                   xlim  = NULL, ylim  = NULL, arrow.len = 0.1, ...)

### Arguments

`x` | The `biplot`, a fitted object. For `biplot.default`, the first set of points (a two-column matrix), usually associated with observations.
`y` | The second set of points (a two-column matrix), usually associated with variables.
`var.axes` | If `TRUE` the second set of points have arrows representing them as (unscaled) axes.
`col` | A vector of length 2 giving the colours for the first and second set of points respectively (and the corresponding axes). If a single colour is specified it will be used for both sets.
`cex` | The character expansion factor used for labelling the points. The labels can be of different sizes for the two sets by supplying a vector of length two.
`xlabs` | A vector of character strings to label the first set of points: the default is to use the row dimname of `x`, or `1:n` is the dimname is `NULL`.
`ylabs` | A vector of character strings to label the second set of points: the default is to use the row dimname of `y`, or `1:n` is the dimname is `NULL`.
`expand` | An expansion factor to apply when plotting the second set of points relative to the first. This can be used to get the two sets on to a physically comparable scale.
`arrow.len` | The length of the arrow heads on the axes plotted in `var.axes` is true. The arrow head can be suppressed by `arrow.len = 0`.

### Details

A biplot is plot which aims to represent both the observations and variables of a matrix of multivariate data on the same plot. There are many variations on biplots (see the references) and perhaps the most widely used one is implemented by `biplot.princomp`. The function `biplot.default` merely provides the underlying code to plot two sets of variables on the same figure.

Graphical parameters can also be given to `biplot`.

### Side Effects

a plot is produced on the current graphics device.

### Author(s)

B.D. Ripley

### References

K. R. Gabriel (1971). The biplot graphical display of matrices with application to principal component analysis. Biometrika 58, 453–467.

J.C. Gower and D. J. Hand (1996). Biplots. Chapman & Hall.

### See Also

`biplot.princomp`, also for examples.

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