colname refered by a variable

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try this ..

df[,colnames(df)==paste("A","C",sep="")]
Hello,

I tried to use a?variable to refer colname, but I got error, could anyone give me advice?

df=data.frame(cbind(AB=1:3,AC=3:5))
df$AC
[1] 3 4 5
df$paste("A","C",sep="")
Error: attempt to apply non-function

thanks
Jian

? ? ? ?[[alternative HTML version deleted]]

______________________________________________
R-help at r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.

Or simpler:
df[, paste("A","C",sep="")]
df[[paste("A","C",sep="")]]

Or:
x <- paste("A","C",sep="")
df[,x]
df[[x]]

Btw, you don't need to use cbind(), data.frame() does it already

Ivan

Le 12/3/2010 08:21, Santosh Srinivas a ?crit :
try this ..

df[,colnames(df)==paste("A","C",sep="")]

On Fri, Dec 3, 2010 at 12:05 PM, Yuan Jian<jayuan2008 at yahoo.com>  wrote:
Hello,

I tried to use a variable to refer colname, but I got error, could anyone give me advice?

df=data.frame(cbind(AB=1:3,AC=3:5))
df$AC
[1] 3 4 5
df$paste("A","C",sep="")
Error: attempt to apply non-function

thanks
Jian

        [[alternative HTML version deleted]]

______________________________________________
R-help at r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.

Ivan CALANDRA
PhD Student
University of Hamburg
Biozentrum Grindel und Zoologisches Museum
Abt. S?ugetiere
Martin-Luther-King-Platz 3
D-20146 Hamburg, GERMANY
+49(0)40 42838 6231
ivan.calandra at uni-hamburg.de

**********
http://www.for771.uni-bonn.de
http://webapp5.rrz.uni-hamburg.de/mammals/eng/1525_8_1.php
or even shorter
df[,paste("A","C",sep="")]

"Santosh Srinivas" <santosh.srinivas at gmail.com> wrote in message 
news:AANLkTikcJy7BVyfBwUwmRQ4dHg4pBdau+Qh_7+K+bRt2 at mail.gmail.com...
try this ..

df[,colnames(df)==paste("A","C",sep="")]
Hello,

I tried to use a variable to refer colname, but I got error, could anyone 
give me advice?

df=data.frame(cbind(AB=1:3,AC=3:5))
df$AC
[1] 3 4 5
df$paste("A","C",sep="")
Error: attempt to apply non-function

thanks
Jian

[[alternative HTML version deleted]]

______________________________________________
R-help at r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide 
http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.

or even shorter
df[,paste("A","C",sep="")]
Other grepping methods that generalize better to partial matches:

df[ , grep("^AC$", colnames(df))]

df[ grep("^AC$", colnames(df)) ]

--  
David.

"Santosh Srinivas" <santosh.srinivas at gmail.com> wrote in message
news:AANLkTikcJy7BVyfBwUwmRQ4dHg4pBdau+Qh_7+K+bRt2 at mail.gmail.com...
try this ..

df[,colnames(df)==paste("A","C",sep="")]

On Fri, Dec 3, 2010 at 12:05 PM, Yuan Jian <jayuan2008 at yahoo.com>  
wrote:
Hello,

I tried to use a variable to refer colname, but I got error, could  
anyone
give me advice?

df=data.frame(cbind(AB=1:3,AC=3:5))
df$AC
[1] 3 4 5
df$paste("A","C",sep="")
Error: attempt to apply non-function

thanks
Jian
David Winsemius, MD
West Hartford, CT