[R] extract columns using their names
Adrian Dusa
adi at roda.ro
Thu May 27 16:35:49 CEST 2004
Right...
As was under the impression that, if I dind't attach the dataframe, I
have to use data1$XX, data1$YY and so on.
I tried
data2 <- data1[, c("data1$XX","data1$YY","data1$ZZ")]
I see my error now.
Thank you very much,
Adrian
-----Original Message-----
From: Eric Lecoutre [mailto:lecoutre at stat.ucl.ac.be]
Sent: Thursday, May 27, 2004 5:27 PM
To: adi at roda.ro
Cc: r-help at stat.math.ethz.ch
Subject: Re: [R] extract columns using their names
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)
>1, Schitu Magureanu Bd.
>050025 Bucharest sector 5
>Romania
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Eric Lecoutre
UCL / Institut de Statistique
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tel: (+32)(0)10473050
lecoutre at stat.ucl.ac.be http://www.stat.ucl.ac.be/ISpersonnel/lecoutre
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