[R] how to "singlify" entries

[Petr Pikal]

Hallo

On 30 May 2005 at 9:15, zhihua li wrote:

> hi netters
> 
> I have a rather simple question.  I have a data frame with two

Well, I do not understand you simple question fully. You have 
something like that

dat<-data.frame(X=1:100, Y=sample(1:10,10))
dat$X<-factor(dat$X)
dat$Y<-factor(dat$Y)
dat$Y[5]<-10

> variables X and Y, both of which are factors. X has 100 levels while Y
> has 10 levels only. The data frame has 100 rows in all, so for X the
> values are unique, and Y has many replicate values.  Now I wanna
> reduce the data frame into 10 rows only, according to the 10 levels of
> Y.  I don't care which value of X is in the same row with Y in the
> final data frame, as long as it is in agreement with the original data
> frame.

Do you want to choose only some rows from your data frame to 
get unique Y and any corresponding X?

dat[!duplicated(dat$Y),]

Or do you want something different?

HTH
Petr

> 
> I think this task can be carried out with some function like
> aggregate. but I failed in figuring it out. Could anybody give me a
> hint?
> 
> Thanks a lot!
> 
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Petr Pikal
petr.pikal at precheza.cz