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JAGS models


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Hi All, 

I'm currently in the process of running ZIP models in rjags to test some hypotheses about duck pair abundance. The zero-inflated models include only an intercept parameter and then 3 different dummy parameters to represent the wetland cover class variables 2, 3, and 4. In theory, one would expect the non-transformed value of the parameter estimates to decrease in value from cover class 1 to 4 sequentially. I'm seeing this trend in the MLE models we ran first actually:

(Intercept)       WCCone     WCCthree       WCCtwo  

    -6.4537       6.0062       0.8016       3.5753   

Unfortunately, I'm running up against a bit of a snag in rjags. The parameter estimates for the wetland cover classes in the zero-inflated portion of the model all end up being relatively the same (~-7 - -8) and are truncated at -10 (see the not-so-nice looking trace plots in attached word file: a2,a3,a4).  I've checked for correlations among the covariates, mistakes in the data, and at this point, I am concerned that this might be a coding problem. I realize this is somewhat of an inane question to ask, however, I'm unfortunately not in an academic lab where I can easily find a fellow JAGS coder, so usually end up having to turn to sources like these if I want a second set of eyes. So, I'm hoping there's someone out there who is willing to look through the attached code and let me know if they see an error that might be causing these weird results. I've literally spent the last 6 months digging through these data and this code so I think my eyes cross every time I look at it. Any help would be great. Thanks, 








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