Re: [Bugs-r-devel] R2WinBUGS bug fix

[Anon. <bob...@he...>]

Uwe Ligges wrote:
> I think this was proposed by Andrew Gelman in the original code and I=20
> already had the discussion but forgot the outcome (people would like to=
=20
> have it randomized?, Andrew?).
>
> Anyway, a fix would be to add drop =3D FALSE as in
>
>    sims <- sims [sample(n.sims), , drop =3D FALSE] # scramble (for=20
> convenience in analysis)
>
>  =20
I'm curious - how can you check for convergence if the order is=20
randomised?  I'm thinking of cases where both chains are moving in the=20
same direction towards the part of the posterior with high probability=20
mass.  It also makes mixing more difficult to assess, although this is=20
less critical.

I would certainly prefer not to have this randomised - there are=20
disadvantage, and if you want the results randomise, it's easy to do=20
(hey, it's one line of code!).  OTOH, if it's already randomised, it's=20
difficult to impossible to unscramble it.

Bob

--=20
Bob O'Hara
Department of Mathematics and Statistics
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