Message-ID: <87293827-7A5B-4EF1-B143-4E4068913E1D@comcast.net>
Date: 2010-12-03T14:13:05Z
From: David Winsemius
Subject: colname refered by a variable
In-Reply-To: <idacdf$7bv$1@dough.gmane.org>
On Dec 3, 2010, at 4:14 AM, Keith Jewell wrote:
> or even shorter
> df[,paste("A","C",sep="")]
Other grepping methods that generalize better to partial matches:
df[ , grep("^AC$", colnames(df))]
df[ grep("^AC$", colnames(df)) ]
--
David.
>
>
> "Santosh Srinivas" <santosh.srinivas at gmail.com> wrote in message
> news:AANLkTikcJy7BVyfBwUwmRQ4dHg4pBdau+Qh_7+K+bRt2 at mail.gmail.com...
> try this ..
>
> df[,colnames(df)==paste("A","C",sep="")]
>
> On Fri, Dec 3, 2010 at 12:05 PM, Yuan Jian <jayuan2008 at yahoo.com>
> wrote:
>> Hello,
>>
>> I tried to use a variable to refer colname, but I got error, could
>> anyone
>> give me advice?
>>
>>> df=data.frame(cbind(AB=1:3,AC=3:5))
>>> df$AC
>> [1] 3 4 5
>>> df$paste("A","C",sep="")
>> Error: attempt to apply non-function
>>
>> thanks
>> Jian
David Winsemius, MD
West Hartford, CT