screeplot               package:stats               R Documentation

Screeplots

Description:

     'screeplot.default' plots the variances against the number of the
     principal component. This is also the 'plot' method for classes
     '"princomp"' and '"prcomp"'.

Usage:

     ## Default S3 method:
     screeplot(x, npcs = min(10, length(x$sdev)),
               type = c("barplot", "lines"),
               main = deparse(substitute(x)), ...)

Arguments:

       x: an object containing a 'sdev' component, such as that
          returned by 'princomp()' and 'prcomp()'.

    npcs: the number of components to be plotted.

    type: the type of plot.

main, ...: graphics parameters.

References:

     Mardia, K. V., J. T. Kent and J. M. Bibby (1979). _Multivariate
     Analysis_, London: Academic Press.

     Venables, W. N. and B. D. Ripley (2002). _Modern Applied
     Statistics with S_, Springer-Verlag.

See Also:

     'princomp' and 'prcomp'.

Examples:

     require(graphics)

     ## The variances of the variables in the
     ## USArrests data vary by orders of magnitude, so scaling is appropriate
     (pc.cr <- princomp(USArrests, cor = TRUE))  # inappropriate
     screeplot(pc.cr)

     fit <- princomp(covmat=Harman74.cor)
     screeplot(fit)
     screeplot(fit, npcs=24, type="lines")

