On Dec 3, 2010, at 4:14 AM, Keith Jewell wrote:

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.srini...@gmail.com> wrote in message
news:aanlktikcjy7bvyfbwuwmrq4dhg4pbdau+qh_7+k+b...@mail.gmail.com...
try this ..

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

On Fri, Dec 3, 2010 at 12:05 PM, Yuan Jian <jayuan2...@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

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