[R] help with apply, please

[Adrian DUSA]

On Saturday 19 November 2005 22:09, Gabor Grothendieck wrote:
> Getting back to your original question of using apply, solving the LP
> gives us the number of components in any minimal solution and
> exhaustive search of all solutions with that many components can
> be done using combinations from gtools and apply like this:
>
> library(gtools) # needed for combinations
> soln <- lp("min", rep(1,3), rbind(t(mtrx)), rep(">=", 4),
> rep(1,4))$solution k <- sum(soln)
> m <- nrow(mtrx)
> combos <- combinations(m,k)
> combos[apply(combos, 1, function(idx) all(colSums(mtrx[idx,]))),]
>
> In the example we get:
>
>      [,1] [,2]
> [1,]    1    3
> [2,]    2    3
>
> which says that rows 1 and 3 of mtrx form one solution
> and rows 2 and 3 of mtrx form another solution.

I'm speechless.
It is exactly what I needed.
A billion of thanks!
Adrian

-- 
Adrian DUSA
Romanian Social Data Archive
1, Schitu Magureanu Bd
050025 Bucharest sector 5
Romania
Tel./Fax: +40 21 3126618 \
          +40 21 3120210 / int.101