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

[Uwe Ligges]

Constantinos Antoniou wrote:
> Hello,
> 
> 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   ]
> 
> 
> library(e1071)
> lala <- read.csv("station-1-120103.txt",header=F)
> ll <- cbind(lala$V25,lala$V22)
> num.of.clust=50
> assign(paste("cmeans",num.of.clust,sep=""),cmeans(ll,num.of.clust))
> 
> and sure enough if I type cmeans50 I get the output of this cmeans run.
> 
> This also works, naturally:
> 
> llc<-cbind(ll,cmeans50$cluster)
> 
> [and I now get three columns, where the third column is the cluster ID.]
> 
> However, when I do what I really want (i.e. not call cmeans50  
> explicitly, but through the name that I constructed programmatically):
> 
> llc <- cbind(ll,(paste("cmeans",num.of.clust,sep=""))$cluster)

This is a FAQ: use get()

Uwe Ligges


> I only get two columns (the last term has no effect).
> 
> Any ideas as to what I am doing wrong?
> 
> Thanks a lot!
> 
> Costas
> 
> 
>