[R] MCMC object indexing

Ben Bolker bbolker at gmail.com
Thu Jan 20 15:10:08 CET 2011


Robinson, David G <drobin <at> sandia.gov> writes:

> 
> I have an mcmc object and I'm trying to plot the quantiles of the 
> variables - and not as a function of the
> iterations as in cumuplot.
> 
> I cannot seem to find the right combination of indexing to 
> access the variables; after which I'm sure I can
> plot all the statistics I could hope for.
> 
> Any hints for accessing the mcmc object would be appreciated.
> 
> =Dave

  A reproducible example would be very useful.  In general
I find that I can just index an mcmc object as though it
were a matrix, e.g.:

z <- cbind(a=runif(20),b=runif(20),c=runif(20))
library(coda)
m <- mcmc(data=z)
t(apply(m,2,quantile,c(0.025,0.975)))

  If that sort of thing doesn't work for you, please
post an example of what doesn't work ...

  Ben Bolker



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