Plot of the Variances of Derived Variables
DESCRIPTION:
Produces a barplot of the variances of the derived variables.

This function is generic (see Methods); method functions can be written to handle specific classes of data. Classes which already have methods for this function include: princomp.

USAGE: 
screeplot(object, ...)
screeplot.princomp(object, variables=<<see below>>, cumulative=T,
                   main, ...)
REQUIRED ARGUMENTS:
object:
an object having a class for which screeplot has a method.
OPTIONAL ARGUMENTS:
variables:
integer vector telling which variables are to be plotted. The default is to plot the first 10 variables or all the variables if there are less than 10.
cumulative:
logical flag: if TRUE, the cumulative fraction of the variance is printed above each bar in the plot.
main:
character string giving the title of the plot. The default is the name of object.
...:
additional graphics parameters may be given.
VALUE:
invisible vector of the x-coordinates of the centers of the bars.
SIDE EFFECTS:
a plot is produced on the current graphics device.
SEE ALSO:
plot.loadings , princomp .
EXAMPLES: 
longley.pc <- princomp(longley.x, cor=T)
screeplot(longley.pc)