[R] counting strings of identical values in a matrix
A M Lavezzi
lavezzi at unipa.it
Thu Nov 15 17:18:12 CET 2007
Dear Marc
thank you so much!
One thing: writing xx=[1,2,1,1] is not a typo: I
read it as the count of runs of different length starting from 1.
In "prova" I have 1 run of length one, 2 runs of
length two, 1 run of length three and 1 run of length four.
Can I abuse of your time and ask how to do this?
Thanks again
Mario
At 16.48 15/11/2007, you wrote:
>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
===============================
Andrea Mario Lavezzi
Dipartimento di Studi su Politica Diritto e Società
Piazza Bologni 8
90134 Palermo
tel. ++39 091 6625600
fax ++39 091 6112023
skype: lavezzimario
email: lavezzi at unipa.it
web: http://www.unipa.it/~lavezzi
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