[R] paired samples, matching rows, merge()

[Gabor Grothendieck]

On Fri, Aug 20, 2010 at 9:33 AM, Gabor Grothendieck
<ggrothendieck at gmail.com> wrote:
> On Fri, Aug 20, 2010 at 9:27 AM, Cecilia Carmo <cecilia.carmo at ua.pt> wrote:
>> It wasn't the merge command. It doesn't create the variable x3.
>>
>> Cecília
>>
>>
>
> How about:
>
> x$k3 <- with(x, unlist(tapply(k1, k1, seq_along)))
> y$k3 <- with(y, unlist(tapply(k1, k1, seq_along)))
>

And here is a second one in case that one overflows as well:

x$k3 <- with(x, seq_along(k1) - match(k1, k1) + 1)
y$k3 <- with(y, seq_along(k1) - match(k1, k1) + 1)

Note that this one assumes that the data frame is sorted by k1 which
in your example it is.