On Thu, 2007-11-15 at 15:51 +0100, A M Lavezzi wrote:
> Hello
>
> I have this problem. I have a large matrix of this sort:
>
> > prova
> [,1] [,2] [,3] [,4]
> [1,] 3 3 3 3
> [2,] 3 3 3 1
> [3,] 1 3 3 3
> [4,] 1 1 1 3
> [5,] 3 1 1 3
> [6,] 3 1 1 3
> [7,] 1 3 1 3
> [8,] 1 3 3 3
>
> What I want to do is to count the number of
> sequences of ones and stack the results in a
> vector, which I will subsequently use to build an istogram (or a density)
>
> I mean: in the matrix "prova" I have two
> sequences of length two in column 1, one sequence
> of length three in column 2, one sequence of
> length four in column 3 and one sequence of
> length one in column 4. (I know I can actually
> turn the matrix into a vector by using rep(prova))
>
> I would like to get to a vector such as : xx = [1,2,1,1]
I presume a typo above and that it should be:
xx = [2,1,1,1]
?
If so:
> unlist(lapply(apply(prova, 2, rle),
function(x) length(x$lengths[x$values == 1])))
[1] 2 1 1 1
See ?rle to get the basics of identifying runs of values.
HTH,
Marc Schwartz
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