[R] hclust too slow?

[Charles C. Berry]

On Tue, 17 Nov 2009, akonla wrote:

>
> Hi,
>
> I am new to clustering in R and I have a dataset with approximately 17,000
> rows and 8 columns with each data point a numerical character with three
> decimal places.  I would like to cluster the 8 columns so that I get a
> dendrogram as an output.  So, I am simply creating a distance matrix of my
> data, using the 'hclust' function, and then plotting the results (see below,
> my data is contained in the text file).
>
> x<-read.table('SEP_IR_1113_3.txt', header=TRUE,sep="\t')
> x.dist=dist(x)


See

 	?dist

which explains


      This function computes and returns the distance matrix computed by
      using the specified distance measure to compute the distances
      between the rows of a data matrix.

You are trying to cluster 17,000 rows.

No wonder it (dist) is taking its time!

Chuck

> hc=hclust(x.dist,method="average")
> plot(hc, hang=-1)
>
> Unfortunately, the hclust function, although it produces no error terms,
> takes a very long time to run  (>4 hours) and my computer kills the program
> before it finishes.  I don't think this data set is so large to cause such a
> long computing time, and I have plenty of memory since I am running this
> analysis on our university computing cluster.
>
> Has anyone run into this problem before and does anyone have any tips on how
> I can speed up processing?  I can provide extra information if necessary
> regarding my problem.
>
> Thank you!
> -- 
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>
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Charles C. Berry                            (858) 534-2098
                                             Dept of Family/Preventive Medicine
E mailto:cberry at tajo.ucsd.edu	            UC San Diego
http://famprevmed.ucsd.edu/faculty/cberry/  La Jolla, San Diego 92093-0901