[R] Simple but elusive - expand back from counts

[Joshua Wiley]

Hi,

You can use rep() to repeat the appropriate rows as in V4.  For example:

tmp[rep(rownames(tmp), tmp$V4), ]

    V1 V2  V3 V4
1   44 10 abc  1
2   44 10 def  1
3   44 12 abc  2
3.1 44 12 abc  2

if you wanted, you could then reset the row names to NULL to get 1, 2,
3, 4 rather than 3, 3.1

rownames(tmp) <- NULL ## AFTER saving the expanded form.

Cheers,

Josh

On Tue, Mar 29, 2011 at 11:15 AM, jjap <sabjap at gmail.com> wrote:
> Dear R-users,
>
> This should be simple but still eludes me:
>
> Given the following
> tmp<-as.data.frame(matrix(c(44, 10, "abc", 1, 44, 10, "def", 1, 44, 12,
> "abc", 2), 3, 4, byrow=T))
>
> I want to  expand the data to the following form:
>
>  V1 V2  V3 V4
> 1 44 10 abc  1
> 2 44 10 def  1
> 3 44 12 abc  1
> 4 44 12 abc  1
>
> The last row of the original df was duplicated the row by the number in the
> 4th column (which could be expendable being all ones)
> I clumsily tried a few variants of a loop but I am not making any progress.
> Any hints would be greatly appreciated.
> for (i in 1:3){
>  rbind(rep(tmp[i,], temp[i,4])
>  }
>
> --
> View this message in context: http://r.789695.n4.nabble.com/Simple-but-elusive-expand-back-from-counts-tp3415727p3415727.html
> Sent from the R help mailing list archive at Nabble.com.
>
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>



-- 
Joshua Wiley
Ph.D. Student, Health Psychology
University of California, Los Angeles
http://www.joshuawiley.com/