[R] a syntax question: $V100

[Liaw, Andy]

x[,20] or x[[20]] will give you the 20th column of the data frame.  Things
like these are covered in `An Introduction to R'.

If the column names are not necessarily in order, you can always use
something like x[[paste("V", 20, sep="")]].

Andy

> From: WeiWei Shi
> 
> Hi, there:
> 
> I have a syntax question. I have a dataset x with 100 variables. I did
> not set the column name so I used x$V1...x$V100. For my case, I need
> to put the number (e.g. 20) into another variable, like index so that
> I can refer to x$V20 by using something like x$V(index) but I don't
> know how to do that in R.
> 
> thanks,
> 
> Ed
> 
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