[R] grouping similar column values into a single row

[Gabor Grothendieck]

See ?tapply

> tapply(paste(DF$col2), DF$col1, c)
$`mir-1`
[1] "aaa" "abc" "aac"

$`mir-2`
[1] "abb" "aaa"

$`mir-3`
[1] "cag" "ccc" "aaa"

> # or
> t(t(tapply(paste(DF$col2), DF$col1, paste, collapse = " ")))
      [,1]
mir-1 "aaa abc aac"
mir-2 "abb aaa"
mir-3 "cag ccc aaa"

> # or
> t(do.call(cbind, tapply(paste(DF$col2), DF$col1, ts)))
      [,1]  [,2]  [,3]
mir-1 "aaa" "abc" "aac"
mir-2 "abb" "aaa" NA
mir-3 "cag" "ccc" "aaa"


On Sun, Nov 30, 2008 at 1:08 PM, T Joshi <tejalonline at gmail.com> wrote:
> Hi,
> I have a following situation with data:
> col1   col2
> mir-1 aaa
> mir-1 abc
> mir-1 aac
> mir-2 abb
> mir-2 aaa
> mir-3 cag
> mir-3 ccc
> mir-3 aaa
>
> I want to have  output in this format:
> col1     col2
> mir-1 aaa, abc, aac
> mir-2 abb, aaa
> mir-3 cag,ccc,aaa
>
>
> I have sorted column 1 so that the grouping could be possible. I could
> have done the same with mysql using a simple query, but I am not sure
> how I can do it in R. Please suggest me possible way.
>
> Thanks,
> Joshi
>
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