[R] counting strings of identical values in a matrix
Gabor Grothendieck
ggrothendieck at gmail.com
Thu Nov 15 18:35:27 CET 2007
We can append a row of 0's to handle that case:
with(rle(as.vector(rbind(prova, 0))), table(lengths[values == 1]))
On Nov 15, 2007 11:36 AM, Marc Schwartz <marc_schwartz at comcast.net> wrote:
> Ah...OK. I misunderstood then. I thought that you wanted the number of
> runs of 1's in each column.
>
> This is actually easier, _if_ there is not an overlap of 1's from the
> end of one column to the start of the next column:
>
> res <- rle(as.vector(prova))
>
> > res
> Run Length Encoding
> lengths: int [1:11] 2 2 2 2 3 3 5 4 2 1 ...
> values : int [1:11] 3 1 3 1 3 1 3 1 3 1 ...
>
> > table(res$lengths[res$values == 1])
>
> 1 2 3 4
> 1 2 1 1
>
>
> HTH,
>
> Marc
>
>
>
> On Thu, 2007-11-15 at 17:18 +0100, A M Lavezzi wrote:
> > 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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