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

jim holtman jholtman at gmail.com
Fri Oct 24 02:56:32 CEST 2008

```do 'str(myx)' and you will probably see that 'x2' is a factor even
though it appears to be numeric when you print it.  To convert it to
numeric, you can do:

myx\$x2 <- as.numeric(as.character(myx\$x2))

On Thu, Oct 23, 2008 at 8:52 PM, Srinivas Iyyer
<srini_iyyer_bio at yahoo.com> wrote:
> 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
>> 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?
>
>
>
>

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

What is the problem that you are trying to solve?

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