screeplot                package:mva                R Documentation

Screeplot of PCA Results

Description:

     `screeplot' plots the variances against the number of the
     principal component. This is also the `plot' method for class
     `"princomp"'.

Usage:

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

Arguments:

       x: an object of class `"princomp"', as from `princomp()'.

    npcs: the number of principal 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 (1997, 9). Modern Applied
     Statistics with S-PLUS, Springer-Verlag.

See Also:

     `princomp'.

Examples:

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

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

