[R] column wise paste of data.frames

[Dimitris Rizopoulos]

try this:

data("Orthodont", package = "nlme")
metaFields <- c("Subject", "Sex")
Orthodont$ID <- do.call("paste", c(Orthodont[metaFields], sep = "/"))


I hope it helps.

Best,
Dimitris

----
Dimitris Rizopoulos
Biostatistical Centre
School of Public Health
Catholic University of Leuven

Address: Kapucijnenvoer 35, Leuven, Belgium
Tel: +32/(0)16/336899
Fax: +32/(0)16/337015
Web: http://med.kuleuven.be/biostat/
     http://perswww.kuleuven.be/dimitris_rizopoulos/


----- Original Message ----- 
From: "Sebastian Weber" <sebastian.weber at physik.tu-darmstadt.de>
To: <r-help at r-project.org>
Sent: Friday, July 18, 2008 9:36 AM
Subject: [R] column wise paste of data.frames


> Hi everybody!
>
> I'm sure that I overlook something and feel quite stupid to ask, but 
> I
> have not found an easy solution to the following problem: Take e.g. 
> the
> Orthodont data from the nlme package:
>
>> head(Orthodont)
> Grouped Data: distance ~ age | Subject
>  distance age Subject  Sex
> 1     26.0   8     M01 Male
> 2     25.0  10     M01 Male
> 3     29.0  12     M01 Male
> 4     31.0  14     M01 Male
> 5     21.5   8     M02 Male
> 6     22.5  10     M02 Male
>
> Suppose now, that I have a vector which contains the names of the
> "meta"-fields in this data-frame:
>
> metaFields <- c("Subject", "Sex")
>
> I now would like to form a new column "ID" which consists of the 
> columns
> in metaFields joined like the following:
>
>> head(Orthodont)
> Grouped Data: distance ~ age | Subject
>  distance age Subject  Sex  ID
> 1     26.0   8     M01 Male  M01/Male
> 2     25.0  10     M01 Male  M01/Male
> 3     29.0  12     M01 Male  M01/Male
> 4     31.0  14     M01 Male  M01/Male
> 5     21.5   8     M02 Male  M02/Male
> 6     22.5  10     M02 Male  M02/Male
>
> Any paste commands I tried so far failed, e.g.:
>
> Orthodont$ID <- paste(Orthodont[,metaFields], sep="/")
>
> is simply wrong. Ok, I could add the columns within a loop to ID, 
> but
> that is not very elegant. Instead, what I need is a command that in
> effect produces the output of
>
> Orthodont$ID <- paste(Orthodont[,metaFields[1]],
>                      Orthodont[,metaFields[2]] , sep="/")
>
> There should be some way to do it in R - can someone please 
> enlighten
> me? Thanks a lot in advance.
>
> Greetings,
>
> Sebastian
>
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