# Re: [R] Making a markov transition matrix

From: Ingmar Visser <I.Visser_at_uva.nl>
Date: Mon 23 Jan 2006 - 20:45:57 EST

Ajay,
On a similar note, there are two other packages as well for similar models: hmm.discnp for hidden Markov models of univariate discrete non-parametric distributions and depmix for hidden Markov models for multivariate data, ie gaussians, multinomials etc, and combinations of these hth, ingmar

>
> Ajay--you seem to have gotten your question answered regarding putting your
> dataframe in the correct format, etc. If you haven't already, you might
> want to check out the MSM package for multi-state Markov and hidden Markov
> models in continuous time. It's been quite useful for some of my work
> regarding estimating Markov chains/matrices and is actively maintained.
>
>
> Thanks,
> Charles
>
> <<< you wrote >>>
>
> Folks,
>
> I am holding a dataset where firms are observed for a fixed (and
> small) set of years. The data is in "long" format - one record for one
> firm for one point in time. A state variable is observed (a factor).
>
> I wish to make a markov transition matrix about the time-series
> evolution of that state variable. The code below does this. But it's
> hardcoded to the specific years that I observe. How might one
> generalise this and make a general function which does this? :-)
>
> -ans.
>
>
>
> set.seed(1001)
>
> # Raw data in long format --
> raw <- data.frame(name=c("f1","f1","f1","f1","f2","f2","f2","f2"),
> year=c(83, 84, 85, 86, 83, 84, 85, 86),
> state=sample(1:3, 8, replace=TRUE)
> )
> # Shift to wide format --
> fixedup <- reshape(raw, timevar="year", idvar="name", v.names="state",
> direction="wide")
> # Now tediously build up records for an intermediate data structure
> try <- rbind(
> data.frame(prev=fixedup\$state.83, new=fixedup\$state.84),
> data.frame(prev=fixedup\$state.84, new=fixedup\$state.85),
> data.frame(prev=fixedup\$state.85, new=fixedup\$state.86)
> )
> # This is a bad method because it is hardcoded to the specific values
> # of "year".
> markov <- table(destination\$prev.state, destination\$new.state)
>
> --
> Ajay Shah http://www.mayin.org/ajayshah
>
> ajayshah@mayin.org
> http://ajayshahblog.blogspot.com
> <*(:-? - wizard who doesn't know the answer.
>
>
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>
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