[R] extract columns using their names

[Eric Lecoutre]

Hello,

I dont clearly see why you have a problem... What you have to us works 
perfectly.

» mat=diag(3)
» colnames(mat)=letters[1:3]
» mat
      a b c
[1,] 1 0 0
[2,] 0 1 0
[3,] 0 0 1
» mat[,c("a","c")]
      a c
[1,] 1 0
[2,] 0 0
[3,] 0 1

Only condition is to have *set* the names if those columns. See 'colnames' 
or 'dimnames' for that.

Eric

At 16:19 27/05/2004, you wrote:
>Hello,
>Is there a way to extract multiple columns from a dataframe using their
>names instead of their numbers?
>Currently I use:
>data2 <- data1[, c(1,3,9)]
>And I am looking for something like
>data2 <- data1[, c("XX","YY","ZZ")]
>I use the same dataframe for many purposes, and I run codes that change
>the order of the columns every time.
>Many thanks,
>Adrian
>
>~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>Adrian Dusa (adi at roda.ro)
>Romanian Social Data Archive (www.roda.ro)
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Eric Lecoutre
UCL /  Institut de Statistique
Voie du Roman Pays, 20
1348 Louvain-la-Neuve
Belgium

tel: (+32)(0)10473050
lecoutre at stat.ucl.ac.be
http://www.stat.ucl.ac.be/ISpersonnel/lecoutre

If the statistics are boring, then you've got the wrong numbers. -Edward 
Tufte