[R] Simple but elusive - expand back from counts

[Petr Savicky]

On Tue, Mar 29, 2011 at 11:15:33AM -0700, jjap 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)

Hi.

Try the following.

  tmp1 <- tmp[rep(1:nrow(tmp), times=tmp$V4), ]
  tmp1$V4 <- 1
  row.names(tmp1) <- NULL
  tmp1

    V1 V2  V3 V4
  1 44 10 abc  1
  2 44 10 def  1
  3 44 12 abc  1
  4 44 12 abc  1

Hope this helps.

Petr Savicky.