[R] plot clusters

[Christian Hennig]

Hi,

On Sat, 26 Apr 2003, Martin Maechler wrote:

> >>>>> "pingzhao" == pingzhao  <pingzhao at waffle.cs.dal.ca>
> >>>>>     on Fri, 25 Apr 2003 16:45:19 -0300 writes:
> 
>     pingzhao> Hi,
>     pingzhao> I have a dataset which has more than two clusters (say 3 clusters).
>     pingzhao> I used kmeans to cluster the dataset.
> 
>     pingzhao> I am wondering how I can plot the clustering result on a two-dimensional
>     pingzhao> figure????
> 
>     pingzhao> The example in the kmeans help file is as follows:
> 
>     pingzhao> x <- rbind(matrix(rnorm(100, sd = 0.3), ncol = 2),
>     pingzhao>            matrix(rnorm(100, mean = 1, sd = 0.3), ncol = 2))
>     pingzhao> cl <- kmeans(x, 2, 20)
>     pingzhao> plot(x, col = cl$cluster)
> 
>     pingzhao> It seems that this is only working for 2 clusters. When my dataset has more
>     pingzhao> than two clusters, the plot results are obvious wrong.
 
> The much more interesting question is what to do when `x' has
> more than two *dimensions*.
> The easiest is to then plot on the first two principal
> components, but I'm sure Christian Hennig will tell about much
> more sophisticated solutions coming Monday...

...not without being asked explicitly;-)

Christian


-- 
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Christian Hennig
Seminar fuer Statistik, ETH-Zentrum (LEO), CH-8092 Zuerich (currently)
and Fachbereich Mathematik-SPST/ZMS, Universitaet Hamburg
hennig at stat.math.ethz.ch, http://stat.ethz.ch/~hennig/
hennig at math.uni-hamburg.de, http://www.math.uni-hamburg.de/home/hennig/
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