biplot                 package:stats                 R Documentation

Biplot of Multivariate Data

Description:

     Plot a biplot on the current graphics device.

Usage:

     biplot(x, ...)

     ## Default S3 method:
     biplot(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,
            main = NULL, sub = NULL, xlab = NULL, ylab = NULL, ...)

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.  If missing the default colour is looked for in
          the 'palette': if there it and the next colour as used,
          otherwise the first two colours of the palette are used.

     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 tweak the
          scaling of the two sets 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: Limits for the x and y axes in the units of the first set
          of variables.

main, sub, xlab, ylab, ...: 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': the size of
     'xlabs' and 'ylabs' is controlled by 'cex'.

Side Effects:

     a plot is produced on the current graphics device.

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.

