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

[Ista Zahn]

On Mon, Aug 1, 2011 at 1:43 PM, Sarah Goslee <sarah.goslee at gmail.com> wrote:
> Bert,
>
> On Mon, Aug 1, 2011 at 1:27 PM, Bert Gunter <gunter.berton at gene.com> wrote:
>> Folks:
>>
>> I consider my reply below rather clumsy: One has to keep track of
>> index numbers other than that which is inserted and must separately
>> change column names. Is there as "essentially better" way to do this,
>> either via base R or via an R package. I leave it to you to define
>> "essentially better."

A variation on the theme that I prefer for aesthetic reasons is

a <- data.frame(A=1:10, B=11:20, D=31:40, E=41:50)
a$F <- 21:30
a <- a[, c(1:2, 5, 3:4)]

I doubt that it is "essentially better", as it still requires keeping
track of the index, but to me this is easier to follow.

Best,
Ista

>>
> Having tried your solution with sample data, I'd have to agree. :)
> Your approach does mess up the column names, and also doesn't work
> if x is a matrix rather than data frame. Mine, using the full cbind(), works
> in both cases, preserving the column names and running even if x is
> a matrix.
>
> It could be written as a function, but since it's only one line and
> really only requires knowing at what position you'd like to add
> the new column, it hardly seems worth it unless it's something
> to be done repeatedly.
>
>>  x <- data.frame(A=1:3, B=1:3, C=1:3, D=1:3, E=1:3)
>> newcol <- 4:6
>> cbind(x[,1:2], newcol, x[,3:ncol(x)])
>  A B newcol C D E
> 1 1 1      4 1 1 1
> 2 2 2      5 2 2 2
> 3 3 3      6 3 3 3
>>
>>
>> x[,3:6] <- cbind(newcol, x[,3:5])
>> x
>  A B C D E E.1
> 1 1 1 4 1 1   1
> 2 2 2 5 2 2   2
> 3 3 3 6 3 3   3
>>
>>
>> x <- data.frame(A=1:3, B=1:3, C=1:3, D=1:3, E=1:3)
>> x <- as.matrix(x)
>> cbind(x[,1:2], newcol, x[,3:ncol(x)])
>     A B newcol C D E
> [1,] 1 1      4 1 1 1
> [2,] 2 2      5 2 2 2
> [3,] 3 3      6 3 3 3
>> x[,3:6] <- cbind(newcol, x[,3:5])
> Error in x[, 3:6] <- cbind(newcol, x[, 3:5]) : subscript out of bounds
>
> Sarah
>
>> Thanks.
>>
>> Cheers,
>> Bert
>>
>> On Mon, Aug 1, 2011 at 10:17 AM, Bert Gunter <bgunter at gene.com> wrote:
>>> Doesn't work -- you lose column names.
>>>
>>> Try this instead:
>>>
>>> yourframe[,30:51] <- cbind( newcolumn,yourframe[,30:50])
>>>
>>> Adjust column names after via:
>>>
>>> names(yourframe) [30:51] <- c(newcolname,names(yourframe[30:50])
>>>
>>> Cheers,
>>> Bert
>>>
>>> On Mon, Aug 1, 2011 at 10:10 AM, Sarah Goslee <sarah.goslee at gmail.com> wrote:
>>>> x <- cbind(x[,1:29], newcolumn, x[,30:ncol(x)])
>>>>
>>>> On Mon, Aug 1, 2011 at 12:59 PM, Bansal, Vikas <vikas.bansal at kcl.ac.uk> wrote:
>>>>> Dear all,
>>>>>
>>>>> I have a very simple question.I have data frame of 50 columns and i want to insert a column in 30th position.But i do not want to delete that column.Is it possible to include a column in between, so that new values are in 30th column and 30 th column is now 31st and 31st is 32nd......so on and 50th column is 51st..?I will be very thankful to you.
>>>>
> --
> Sarah Goslee
> http://www.functionaldiversity.org
>
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-- 
Ista Zahn
Graduate student
University of Rochester
Department of Clinical and Social Psychology
http://yourpsyche.org