[R] biplot

[Prof Brian Ripley]

On Tue, 20 Nov 2007, S Ellison wrote:

> Also check the asp= parameter in plot.default and plot.window; this sets
> the aspect ratio so that 1 unit in x is the same physicla length as 1
> unit in y. I don;t know whether it is respeced by your particular
> biplot, though.

That's not how biplot.default() does it: rather it always plots a square 
plot within the device window with axes it manages itself and which do 
ensure that the scales are the same in both directions.

I don't understand the request: the two quantities plotted on a 
conventional biplot are dimensionally different, so why would one want 
them to have the same scale?

>>>> Bernardo Rangel Tura <tura at centroin.com.br> 20/11/2007 10:51:12
>>>>
>
> On Mon, 2007-11-19 at 13:51 -0500, Weiwei Shi wrote:
>> Hi,
>>
>> I am wondering how to draw biplot with the same scales on both
> plots?
>> For example, if the two plots have much different scales, generally
>> the two x-y's are scaled so that the two plots are sitting in the
>> center automatically. How to disable this?
>>
>> Thanks
>
> Hi WeiWei
>
> To solve your problem you must use the options xlim, ylim in your
> biplot
>
>
> par(mfrow=c(2,1))
> biplot(...,xlim=c(minimun,maximun),ylim=c(minimun,maximun),...)
> biplot(...,xlim=c(minimun,maximun),ylim=c(minimun,maximun),...)

Hmm: that is two biplots, each two superimposed plots.

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
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