On 2011-03-09 12:14, chris20 wrote:
Hi,
I am trying to understand how the biplot.prcomp is constructed so I can
manipulate it to emphasise particular observations and reduce the number of
variables shown.
The prcomp model I have ran has cor=TRUE and scale=TRUE
I have worked out from looking at str(prcomp.model) that...
prcomp.model$x = the observations ploted in the biplot
prcomp.model$rotation = the variables that form the arrows.
But there appears to be a scaling factor because when I plot
biplot(prcomp.model$rotation, prcomp.model$x)
The biplot is slightly off scale compared with biplot(prcomp.model)
Look at the code; it's pretty short.
You may want to compare:
biplot(prcomp.model, scale=0)
biplot(prcomp.model$x[, 1:2], prcomp.model$rotation[, 1:2])
Peter Ehlers
Under ?biplot.prcomp it talks about lambda^scale and lambda^(1-scale) but I
just can't seem to work it out so that the two biplots look the same. HELP!!
Thanks
Chris
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