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How to determine the length of the required burn-in until convergence in MCMCglmm package or another package

7 messages · Ben Bolker, Jarrod Hadfield, Euis Aqmaliyah

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[please keep r-sig-mixed in Cc:]

  To repeat what I said below, the general brute-force strategy would be

N=2 (or 10 or something)
run MCMCglmm with some reasonably optimistic default settings such that
the final sample size (nitt-nburn)/thin is 1000
while (convergence not satisfactory)
    nitt = N*nitt
    thin = N* thin
    re-try MCMCglmm

This brute force strategy will fail if something is wrong with your
model (e.g. underdetermined).  Strengthening priors may help.  Other
than that, without more information, we really can't help you more.
On 17-03-27 11:19 AM, Euis Aqmaliyah wrote:
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Hi Euis,

In an earlier post you said you were fitting zero-inflated models 
(zipoisson)? Is it possible you

a) forgot to fix the non-identifiable residual variance for the 
zero-inflation process at some value (e.g. 1)?

b) that the data are not zero-inflated but just over-dispersed so the  
zero-inflation parameters are heading off towards -Infinity?

Cheers,

Jarrod
On 27/03/2017 18:40, Ben Bolker wrote:

  
    
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Hi Jarrod,

Zero-Inflated that i meant is not Zero-Inflated Poisson. It is follow a
semicontinuous distribution with a mixture
of zeros and continuously distributed positive values.
But, i have tried to set fix residual variance and the convergence has
reached in two model that i use.
Thank you for your advice.

Regards

Pada tanggal 28 Mar 2017 01.18, "Jarrod Hadfield" <j.hadfield at ed.ac.uk>
menulis:

  
  
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Hi,

If you are not explicitly fitting a zero-inflated model then my 
suggestions are not relevant, and you should not fix the residual 
variance. A description of your data and a post of your model syntax 
would help us diagnose the problem.

Cheers,

Jarrod
On 28/03/2017 13:16, Euis Aqmaliyah wrote:
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Dear Jarrod,

So, because my zero-inflated data is a mixture of zeros and continuosly
diatributed positive values, i use two models, there are linear mixed model
(LMM) for positive values and generalized linear mixed model (GLMM) with
logit as link function for probability of positive values.
In LMM, prior for residual variance that i set is R=list(V=1, nu=0) like
you said in my post a few days ago.
And then, in GLMM, i set fix residual variance.
Is it true?

Regards

Pada tanggal 28 Mar 2017 19.20, "Jarrod Hadfield" <j.hadfield at ed.ac.uk>
menulis:

  
  
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Hi,

Yes - for the binary model you should fix the residual variance.

Cheers,

Jarrod
On 28/03/2017 13:34, Euis Aqmaliyah wrote:
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Okay.
Thank you Jarrod for your help.

Regards

Pada tanggal 28 Mar 2017 19.39, "Jarrod Hadfield" <j.hadfield at ed.ac.uk>
menulis: