[R] concatenating range of columns in dataframe

[Bert Gunter]

I think you need to spend some time with an R tutorial or two,
especially with regard to indexing.

Unless I have misunderstood (apologies if I have),

df$Conc <- apply(df[,-1],1,paste,collapse="")

does it.

-- Bert


Bert Gunter

"The trouble with having an open mind is that people keep coming along
and sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )


On Thu, Mar 9, 2017 at 8:16 PM, Evan Cooch <evan.cooch at gmail.com> wrote:
> Suppose I have the following data frame (call it df):
>
> Trt   y1  y2  y3  y4
> A1A   1    0    0    1
> A1B  1    1    0    0
> A1 C   0   1    0   1
> A1D   1    1    1   1
>
> What I want to do is concatenate columns y1  -> y4 into a contiguous string
> (which I'll call df$conc), so that the final df looks like
>
> Trt      Conc
> A1A   1001
> A1B   1100
> A1C  0101
> A1D   1111
>
>
> Now, if my initial dataframe was simply
>
>  1   0  0  1
>  1   1  0  0
>   0  1  0  1
>   1  1  1  1
>
> then apply(df,1,paste,collapse="") does the trick, more or less.
>
> But once I have a Trt column, this approach yields
>
> A1A1001
> A1B1100
> A1C0101
> A1D1111
>
> I need to maintain the space between Trt, and the other columns. So, I'm
> trying to concatenate a subset of columns in the data frame, but I don't
> want to have to do something like create a cahracter vector of the column
> names to do it (e.g., c("y1","y2","y3","y4"). Doing a few by hand that way
> is easy, but not if you  have dozens to hundreds of columns to work with.
>
>  Ideally, I'd like to be able to say
>
> "concatenate df[,2:4], get rid of the spaces, pipe the concatenated columns
> to a new named column, and drop the original columns from the final df.
>
> Heuristically,
>
> df$conc <- concatenate df[,2:4] # making a new, 5th column in df
> df[,2:4] <- NULL   # to drop original columns 2 -> 4
>
> Suggestions/pointers to the obvious appreciated.
>
> Thanks in advance!
>
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