[R] Inserting column in between -- "better" way?

[peter dalgaard]

On Aug 2, 2011, at 19:17 , Bert Gunter wrote:

> Thanks for this Peter:
> 
>> 
>> Sarah (sic) is on the right track, just lose the commas so that you don't drop to a vector:
>> 
>>> x <- data.frame(A=1:3, B=1:3, C=1:3, D=1:3, E=1:3)
>>> newcol <- 4:6
>>> cbind(x[1], newcol, x[2:ncol(x)])
>>  A newcol B C D E
>> 1 1      4 1 1 1 1
>> 2 2      5 2 2 2 2
>> 3 3      6 3 3 3 3
>> 
> 
> Am I correct in saying that this is a bit subtle: x[1] and
> x[2:ncol(x)] are actually lists with vector components; so you're
> cbinding lists, which retain the labels, no?

Well, to be precise they are obtained by indexing a data frame _as_ a list. The result of that is a data frame (always, which was the point). 

So you're cbind()-ing data frames, which is what you wanted to do all along. 

> 
> If so, it's a nice subtlety to remember, anyway.
> 
> -- Bert
> 
> 
> -- 
> "Men by nature long to get on to the ultimate truths, and will often
> be impatient with elementary studies or fight shy of them. If it were
> possible to reach the ultimate truths without the elementary studies
> usually prefixed to them, these would not be preparatory studies but
> superfluous diversions."
> 
> -- Maimonides (1135-1204)
> 
> Bert Gunter
> Genentech Nonclinical Biostatistics

-- 
Peter Dalgaard, Professor,
Center for Statistics, Copenhagen Business School
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