Re: [R] Help in kmeans

From: Christian Hennig <chrish_at_stats.ucl.ac.uk>
Date: Wed, 06 Apr 2011 13:00:27 +0100 (BST)

I'm not going to comment on column names, but this is just to make you aware that the results of k-means depend on random initialisation.

This means that it is possible that you get different results if you run it several times. It basically gives you a local optimum and there may be more than one of these.
Use set.seed to see whether this explains your problem.

Best regards,
Christian

On Wed, 6 Apr 2011, Raji wrote:

> Hi All,
>
> I was using the following command for performing kmeans for Iris dataset.
>
> Kmeans_model<-kmeans(dataFrame[,c(1,2,3,4)],centers=3)
>
> This was giving proper results for me. But, in my application we generate
> the R commands dynamically and there was a requirement that the column names
> will be sent instead of column indices to the R commands.Hence, to
> incorporate this, i tried using the R commands in the following way.
>
> kmeans_model<-kmeans((SepalLength+SepalWidth+PetalLength+PetalWidth),centers=3)
>
> or
>
> kmeans_model<-kmeans(as.matrix(SepalLength,SepalWidth,PetalLength,PetalWidth),centers=3)
>
> In both the ways, we found that the results are different from what we saw
> with the first command (with column indices).
>
> can you please let us know what is going wrong here.If so, can you please
> let us know how the column names can be used in kmeans to obtain the correct
> results?
>
> Many thanks,
> Raji
>
> --
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>
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https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. Received on Wed 06 Apr 2011 - 12:04:03 GMT

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