[R] how to stack a list of arrays

[R. Michael Weylandt]

Try this for the given data: you'll have to modify the group label
trick a bit if row-numbers aren't even for each element of L, but it's
not hard.

L <- list(`0` = matrix(rnorm(6), ncol = 2), `1` = matrix(rnorm(6),
ncol = 2), `2` = matrix(rnorm(6), ncol = 2))
# Generally it's bad form to use numbers for names

cbind(do.call(rbind, L), group = rep(as.double(names(L)), each = nrow(L[[1]]))

Good luck,
Michael

2011/11/23 Ernest Adrogué <nfdisco at gmail.com>:
> Hello,
>
> I have this list of 2-d arrays:
>
> $`0`
>             k        d
> [1,] 0.2011962 4.019537
> [2,] 0.2020706 5.722719
> [3,] 0.2029451 7.959612
>
> $`1`
>             k        d
> [1,] 0.3148325 2.606903
> [2,] 0.3160287 3.806665
> [3,] 0.3172249 5.419222
>
> $`2`
>             k        d
> [1,] 0.2332536 4.949390
> [2,] 0.2342188 7.115258
> [3,] 0.2351840 9.955909
>
> which I need to transform into a data frame like this one:
>
>             k        d group
> [1,] 0.2011962 4.019537     0
> [2,] 0.2020706 5.722719     0
> [3,] 0.2029451 7.959612     0
> [1,] 0.3148325 2.606903     1
> [2,] 0.3160287 3.806665     1
> [3,] 0.3172249 5.419222     1
> [1,] 0.2332536 4.949390     2
> [2,] 0.2342188 7.115258     2
> [3,] 0.2351840 9.955909     2
>
> Is there any R function that I can use? I know stack() but it only
> works with vectors.
>
> Thank you!
> Ernest
>
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