[本週專題]怎样判断模型收敛？

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模型运行成功，怎样判断是否收敛呢？
知道监测变量服从正态分布，不知道mu和tau，这种情况怎么处理，在程序中该怎么表达？
因变量可以作为随机变量（模型参数）进行监测吗？这样做怎么提示“undefined real result”？
请知道的给解释下，万分感谢！！！

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关键词：判断模型 Undefined Defined DEFINE Result 正态分布 模型

The Error message 'undefined real result' indicates numerical overflow. Possible reasons include:

• Initial values generated from a 'vague' prior distribution may be numerically extreme - specify appropriate initial values;
• Numerically impossible values such as log of a non-positive number - check, for example, that no zero expectations have been given when Poisson modelling;
• Numerical difficulties in sampling.
• 
  
  

Possible solutions include:

• Better initial values;
• More informative priors - uniform priors might still be used but with their range restricted to plausible values;
• Better parameterisation to improve orthogonality;
• Standardisation of covariates to have mean 0 and standard deviation 1.
• 
  

Probit models are particularly susceptible to this problem, i.e. generating undefined real results. If a probit is a stochastic node, it may help to put reasonable bounds on its distribution, e.g.

probit(p) <- delta
delta ~ dnorm(mu, tau)I(-5, 5)
This trap can sometimes be escaped from by simply clicking on the update button. The equivalent construction
   p <- phi(delta)
may be more forgiving.

bugs确实很难学啊