R help - Oct 2008 - finding unique and max value from a data.frame

Hi group, 

How can I identify an element with max value among duplicated elements all in a
data frame

Example:
> x1
  x1 x2
1  a  4
2  b  3
3  c  2
4  a  1
5  c  2
6  f  3
7  g  4
8  f  5


I want to be able to get a data frame with all unique(x1) with max value

  x1 x2
1  a  4
2  b  3
3  c  2
5  c  2
7  g  4
8  f  5


Could I get some help please. 
thanks
srini

?aggregate

  x1 x2
1  a  4
2  b  3
3  c  2
4  a  1
5  c  2
6  f  3
7  g  4
8  f  5
> aggregate(x$x2, list(x$x1), max)
  Group.1 x
1       a 4
2       b 3
3       c 2
4       f 5
5       g 4
>

On Thu, Oct 23, 2008 at 8:30 PM, Srinivas Iyyer
<srini_iyyer_bio at yahoo.com> wrote:
> Hi group,
>
> How can I identify an element with max value among duplicated elements all
in a data frame
>
> Example:
>
>> x1
>  x1 x2
> 1  a  4
> 2  b  3
> 3  c  2
> 4  a  1
> 5  c  2
> 6  f  3
> 7  g  4
> 8  f  5
>
>
> I want to be able to get a data frame with all unique(x1) with max value
>
>  x1 x2
> 1  a  4
> 2  b  3
> 3  c  2
> 5  c  2
> 7  g  4
> 8  f  5
>
>
> Could I get some help please.
> thanks
> srini
>
> ______________________________________________
> 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.
>


-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem that you are trying to solve?

Hi Jim, 
thank you for tip. However, why it works for you and the same line fails  in my
R.
> myx <-x
> myx
  x1 x2
1  a  4
2  b  3
3  c  2
4  a  1
5  c  2
6  f  3
7  g  4
8  f  5
> aggregate(x=myx$x2,by =list(myx$x1),max)
Error in Summary.factor(c(4L, 1L), na.rm = FALSE) : 
  max not meaningful for factors

Thank you.


--- On Thu, 10/23/08, jim holtman <jholtman at gmail.com> wrote:
> From: jim holtman <jholtman at gmail.com>
> Subject: Re: [R] finding unique and max value from a data.frame
> To: srini_iyyer_bio at yahoo.com
> Cc: R-help at stat.math.ethz.ch
> Date: Thursday, October 23, 2008, 8:41 PM
> ?aggregate
> 
>   x1 x2
> 1  a  4
> 2  b  3
> 3  c  2
> 4  a  1
> 5  c  2
> 6  f  3
> 7  g  4
> 8  f  5
> > aggregate(x$x2, list(x$x1), max)
>   Group.1 x
> 1       a 4
> 2       b 3
> 3       c 2
> 4       f 5
> 5       g 4
> >
> 
> 
> On Thu, Oct 23, 2008 at 8:30 PM, Srinivas Iyyer
> <srini_iyyer_bio at yahoo.com> wrote:
> > Hi group,
> >
> > How can I identify an element with max value among
> duplicated elements all in a data frame
> >
> > Example:
> >
> >> x1
> >  x1 x2
> > 1  a  4
> > 2  b  3
> > 3  c  2
> > 4  a  1
> > 5  c  2
> > 6  f  3
> > 7  g  4
> > 8  f  5
> >
> >
> > I want to be able to get a data frame with all
> unique(x1) with max value
> >
> >  x1 x2
> > 1  a  4
> > 2  b  3
> > 3  c  2
> > 5  c  2
> > 7  g  4
> > 8  f  5
> >
> >
> > Could I get some help please.
> > thanks
> > srini
> >
> > ______________________________________________
> > 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.
> >
> 
> 
> 
> -- 
> Jim Holtman
> Cincinnati, OH
> +1 513 646 9390
> 
> What is the problem that you are trying to solve?