[R] Convert timeseries to transition matrix

[Giovanni Petris]

The following, using table, seems to work:

> x <- sample(letters[1:2], 10, replace=T)
> x
 [1] "b" "a" "a" "b" "b" "a" "a" "b" "b" "b"
> table(x[-1],x[-length(x)])
   
    a b
  a 2 2
  b 2 3


Hope this helps,
Giovanni Petris

> Date: Tue, 22 Mar 2005 11:20:40 -0500
> From: Ingmar Visser <i.visser at uva.nl>
> Sender: r-help-bounces at stat.math.ethz.ch
> Cc: 
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> User-Agent: Microsoft-Entourage/11.1.0.040913
> 
> Hi All,
> Does someone have an idea of how to cleverly convert a categorical
> timeseries into a transition matrix?
> Ie, I have something like:
> x<- c(1,1,2,1,1,2,2,2,1,2),
> And I want a matrix with counts and/or probabilities:
> > tr <- matrix(c(2,3,2,2),2,2)
> > tr
>      [,1] [,2]
> [1,]    2    2
> [2,]    3    2
> Meaning that there are two transitions from 1 to 1, two from 1 to 2, three
> from 2 to 1 and two from 2 to 2.
> Using for loops etc this is of course no problem, but I am curious whether
> there is a smarter solution.
> Any hints appreciated, Ingmar
> 
> -- 
> Ingmar Visser
> Department of Psychology, University of Amsterdam
> Roetersstraat 15, room 1009
> 1018 WB Amsterdam
> The Netherlands
> http://users.fmg.uva.nl/ivisser/
> tel: +31-20-5256735
> 
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