R help - Aug 2011 - locate the needed columns

Hi All,

                I have a data frame, whose colnames like "A.x, B.x, C.x,
A.y, B.y, C.y". There could be many columns like this pattern. I want to
compare data in columns A.x with A.y, B.x with B.y and C.x with C.y etc.
Suppose my data frame is d,
names(d) = c("A.x", "B.x", "C.x", "A.y",
"B.y", "C.y");

If I want to
D1 = data.frame(d$A.x, d$A.y);
D2 = data.frame(d$B.x, d$B.y); etc. or do other operation for each pair,


What is elegant way to do it rather than use a loop?

Thanks.

HXD


	[[alternative HTML version deleted]]

If the pattern is characterized by capital letters as your sample
suggests. The following code may help

df<-list()
names(d) = c("A.x", "B.x", "C.x", "A.y",
"B.y", "C.y")
group.v<-matrix(NA,nrow=3,ncol=2) ### you may need to modify nrow and ncol
for (i in 1:3) {
group.v[i,]<-names(d)[grep(LETTERS[i],names(d))]
df[i]<-d[,names(d)%in% group.v[i]]
}


Weidong Gu

On Tue, Aug 30, 2011 at 2:31 PM, Hui Du <Hui.Du at dataventures.com>
wrote:
>
> Hi All,
>
> ? ? ? ? ? ? ? ?I have a data frame, whose colnames like "A.x, B.x,
C.x, A.y, B.y, C.y". There could be many columns like this pattern. I want
to compare data in columns A.x with A.y, B.x with B.y and C.x with C.y etc.
> Suppose my data frame is d,
> names(d) = c("A.x", "B.x", "C.x",
"A.y", "B.y", "C.y");
>
> If I want to
> D1 = data.frame(d$A.x, d$A.y);
> D2 = data.frame(d$B.x, d$B.y); etc. or do other operation for each pair,
>
>
> What is elegant way to do it rather than use a loop?
>
> Thanks.
>
> HXD
>
>
> ? ? ? ?[[alternative HTML version deleted]]
>
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