biplot                  package: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'.

xlim, ylim, ...: graphical parameters.

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.

