[R] getting a variable from an object named using paste

Constantinos Antoniou antoniou at central.ntua.gr
Sat Jul 9 12:53:23 CEST 2005


The subject could be articulated better ;(, but I am stuck...

In any case, my problem is the following: I am trying to use knn, and  
it requires a classification. So I am using cmeans for this. What I  
want to do is add the classification as a new column in my data.frame  
(to be used for knn). Now, the trick is that I would like to name the  
output of the cmeans classification based on the number of clusters  
(e.g. cmeans30 for 30 clusters). To do this, I do the following:

[The file for this example can be downloaded from:

http://mit.edu/costas/www/station-1-120103.txt   ]

lala <- read.csv("station-1-120103.txt",header=F)
ll <- cbind(lala$V25,lala$V22)

and sure enough if I type cmeans50 I get the output of this cmeans run.

This also works, naturally:


[and I now get three columns, where the third column is the cluster ID.]

However, when I do what I really want (i.e. not call cmeans50  
explicitly, but through the name that I constructed programmatically):

llc <- cbind(ll,(paste("cmeans",num.of.clust,sep=""))$cluster)

I only get two columns (the last term has no effect).

Any ideas as to what I am doing wrong?

Thanks a lot!


Constantinos Antoniou, Ph.D.
Department of Transportation Planning and Engineering
National Technical University of Athens
5, Iroon Polytechniou str. GR-15773, Athens, Greece

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