[R] extract columns using their names

[Petr Pikal]

On 27 May 2004 at 17:19, Adrian Dusa 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")]

Hi

Did you try it? Works on R 1.9.0 W2000

> data1<-data.frame(alfa=rnorm(10),beta=rnorm(10,5),gama=rnorm(10,.1))
> data1
          alfa     beta        gama
1  -0.68536013 5.310451  1.55570932
2  -0.43824815 4.998961  0.51348779
3  -1.20083111 4.585788  0.68135905
4  -0.07962607 6.443884  0.05560703
5  -0.03044263 5.355516 -0.16195279
6  -0.19878437 4.142789  0.07888565
7   1.90507619 4.691988  0.88832135
8  -0.51817154 4.844728 -0.80310925
9  -1.19614142 4.457188 -1.00103103
10  0.50957999 6.178542 -1.06628714
> data1[,c("alfa","gama")]
          alfa        gama
1  -0.68536013  1.55570932
2  -0.43824815  0.51348779
3  -1.20083111  0.68135905
4  -0.07962607  0.05560703
5  -0.03044263 -0.16195279
6  -0.19878437  0.07888565
7   1.90507619  0.88832135
8  -0.51817154 -0.80310925
9  -1.19614142 -1.00103103
10  0.50957999 -1.06628714

Cheers
Petr
> 
> 
> 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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Petr Pikal
petr.pikal at precheza.cz