[R] finding unique and max value from a data.frame

[Srinivas Iyyer]

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?