R help - Aug 2011 - how to create data.frames from vectors with duplicates

Hi R users,

suppose I have two vectors,
 > x=c(1,2,3,4,5)
 > y=c('a','b','c','a','c')
How can I get a data.frame like this?
> xy
      count
a     5
b     2
c     8

I know a few ways to fulfill the task. However, I have a huge number
of this kind calculations, so I'd like an efficient solution. Thanks

-- 
Best,
Zhenjiang

Hi Zhenjiang,

Try

table(unlist(mapply(function(x, y) rep(x, y), y, x)))

HTH,
Jorge


On Wed, Aug 31, 2011 at 12:45 PM, zhenjiang xu <> wrote:
> Hi R users,
>
> suppose I have two vectors,
>  > x=c(1,2,3,4,5)
>  > y=c('a','b','c','a','c')
> How can I get a data.frame like this?
> > xy
>      count
> a     5
> b     2
> c     8
>
> I know a few ways to fulfill the task. However, I have a huge number
> of this kind calculations, so I'd like an efficient solution. Thanks
>
> --
> Best,
> Zhenjiang
>
> ______________________________________________
> R-help@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.
>
	[[alternative HTML version deleted]]

Try this:

rowsum(x, y)

On Wed, Aug 31, 2011 at 1:45 PM, zhenjiang xu <zhenjiang.xu at gmail.com>
wrote:
>
> Hi R users,
>
> suppose I have two vectors,
> ?> x=c(1,2,3,4,5)
> ?> y=c('a','b','c','a','c')
> How can I get a data.frame like this?
> > xy
> ? ? ?count
> a ? ? 5
> b ? ? 2
> c ? ? 8
>
> I know a few ways to fulfill the task. However, I have a huge number
> of this kind calculations, so I'd like an efficient solution. Thanks
>
> --
> Best,
> Zhenjiang
>
> ______________________________________________
> 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.


--
Henrique Dallazuanna
Curitiba-Paran?-Brasil
25? 25' 40" S 49? 16' 22" O

On Aug 31, 2011, at 11:45 AM, zhenjiang xu wrote:
> Hi R users,
> 
> suppose I have two vectors,
>> x=c(1,2,3,4,5)
>> y=c('a','b','c','a','c')
> How can I get a data.frame like this?
>> xy
>      count
> a     5
> b     2
> c     8
> 
> I know a few ways to fulfill the task. However, I have a huge number
> of this kind calculations, so I'd like an efficient solution. Thanks

See ?rep and ?as.data.frame.table

Try this:
> data.frame(table(rep(y, x)))
  Var1 Freq
1    a    5
2    b    2
3    c    8

HTH,

Marc Schwartz