The variables are scaled by
$lambda^scale$ and the observations are
scaled by $lambda ^ (1-scale)$ where
lambda are the singular values as computed by
princomp. Normally $0
pc.biplot
If true, use what Gabriel (1971) refers to as a
"principal component biplot", with $lambda = 1$ and
observations scaled up by sqrt(n) and variables scaled down by
sqrt(n). Then the inner products between variables approximate
covariances and distances between observations approximate
Mahalanobis distance.
...
optional arguments to be passed to
biplot.default.
Value
a plot is produced on the current graphics device.
Details
This is a method for the generic function 'biplot'. There is
considerable confusion over the precise definitions: those of the
original paper, Gabriel (1971), are followed here. Gabriel and
Odoroff (1990) use the same definitions, but their plots actually
correspond to pc.biplot = TRUE.