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Questions tagged [winbugs]

Questions about BUGS language for defining Bayesian models that can be run by the WinBUGS software package. It is advised to supplement your question with a reproducible BUGS example (http://stackoverflow.com/q/5963269).

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20 views

Is there something wrong with my Bayesian hierarchical spatio-temporal model?

I built a Bayesian spatio-temporal model and one of the parameters to be estimated is the random spatial effects s. The random spatial effect is assigned an intrinsic conditional autoregressive prior (...
12 views

How to form input parameters for global time trend CAR prior from spatial map (WINBUGS)?

I have a spatiotemporal model found here. In this model, car.normal is used twice, one for spatial areal units: ...
8 views

Pseudo T-stat in Winbugs?

I am trying to obtain the "Pseudo T-stat" in Winbugs for a Poisson Log-normal model. Any suggestion of how can I get that.
39 views

Winbugs code multivariate hierarchical Poisson Log-normal CAR model

I am looking for some example code to develop multivariate hierarchical Poisson Log-normal CAR model using Winbugs. Can anyone help me with similar reserach that added their code? Also, how can I ...
97 views

Are “improper uniform priors” in Bayesian analysis equivalent to maximum likelihood estimations?

The improper uniform distribution for parameter $\theta$ is : $p(\theta)=1,\ for -\infty<\theta<\infty$. It is called "improper" since it does not integrate to 1. Because Bayesian theorem is ...
47 views

Simulating data in JAGS “ones trick”

I am trying to simulate data to use for posterior predictive checks in JAGS running through R, which is relatively simple for pre-loaded distributions, but I am looking to simulate data when I have ...
5 views

How does RJags handle situations in which we have a constraint on combined parameters, but the parameters may take on values outside the constraints?

Suppose we have the following model for the difference in two proportions from a binomial. ...
278 views

How to interpret Zero-Inflated Poisson in WINBUGS?

I have Winbugs code for a zero-inflated Poisson (ZIP) model. I obtained this code from my lab at university and the person who wrote it is not accessible for me to ask questions. Here is the code: <...
54 views

How to interpret zero-inflation model for Bayesian regression?

I am trying to understand the zero-inflated poisson (ZIP) model used in Bayesian regression modelling. I came across code here for the ZIP model. My question is related to the 3rd line of code within ...
54 views

How to specify a new joint prior distribution restricted to (0,1) interval in WinBUGS?

I am doing some Bayesian analysis in OpenBUGS and I need to specify a joint prior distribution for parameters $\gamma_1$ and $\gamma_2$ (the Jeffreys prior related to my model), such that \pi(\...
89 views

How does WINBUGS determine the posterior density of a parameter with multiple chains?

I am a new user to WINBUGS. I am running a model with 2 chains. When my model has finished running I have the following posterior density plot of my parameter: The plot only shows one distribution (i....
70 views

How do interpret a vague prior for hierarchical modeling?

I am new to Bayesian analysis and using the following WINBUGS example to understand Bayesian hierarchical modeling: I have 2 questions: 1) For the fixed effects terms, i.e., the beta0 and beta1 ...
120 views

How to identify prior for the precision parameter in Winbugs

I have the following model: model{ for (i in 1:n){ y[i] ~dnorm(mu[i], tau) mu[i] <- a + b*x[i] } ...
180 views

“Undefined real result” with inverse() function in WinBUGS

Using WinBUGS, I'd like to generate the posterior distribution for a function of several other variables (stochastic nodes). One step in building up this function involves taking the inverse of a ...
161 views

How do I specify a random effect in Bayesian beta regression model?

My response data are proportions that I want to model with one continuous predictor and a random effect of group. Here's my winbugs code: ...
1k views

How do I calculate the posterior predictive distribution in WinBUGS?

I would like to work out the posterior predictive distribution from the following multilevel (mixed effect) model in WinBUGS. The example is taken from an example I found online for illustrative ...
52 views

Winbugs fixed effects stats output: mean or median?

I am running a fixed effects hazard ratios model with WinBUGS and I can't tell if I've run into a potential problem. In the stats output, my mean and median are similar, but generally differ by ...
355 views

Winbugs beta distribution

I have fitted a likelihood function with a dbeta function in WinBUGs as follows ...
97 views

Left or right skewed prior in WinBUGS

I am trying to find a proper way of defining a right or left skewed continuous (0...100) distribution for my priors in a simple linear regression. Furthermore, I expect to find some outliers in my ...
2k views

Bayesian t-test assumptions

I know that the traditional independent t-test assumes homoscedasticity (i.e., equal variances across groups) and normality of the residuals. They are usually checked by using levene's test for ...
61 views

Reference for modeling with WinBugs

Does anyone have any good reference for beginners in WinBUGS about modeling? I already have some familiarity with R, but I had never used R2WinBUGS before. I'm interested in making beta, beta ...
975 views

Learning WinBUGS programming for network meta-analysis

I'm currently interested in learning NMA using WinBUGS. I studied the general concepts behind multiple treatment comparisons and i have a good base on classic pair-wise meta-analysis. I can also do a ...
183 views

Simple explanation of a WinBUGS code

Can anyone give me a quick walkthrough of what this code is doing? I think the line log( mu[i] ) <- alpha + beta * (year[i]-1970) + log( pop[i] ) is updating ...
3k views

WinBUGS error - undefined real result

I am trying to run this WinBUGS code to get a prediction for the number of fatalities in 1975 ...
77 views

Change a random effects model into a fixed effects model in *BUGS

I want to manipulate this RE model into a FE model for sensitivity analysis. The model is described here: Baseline natural history model ...
2k views

Which is the best method for network meta-analysis?

There are now several different approaches to perform a network meta-analysis or mixed treatment comparison. The most commonly used and accessible ones are probably the following: in a Bayesian ...
510 views

Modeling quadratic function parameters as a function of variables

I'm modeling a response variable that varies seasonally. The pattern is relatively well described by a quadratic function. As the data have been collected over many (~50) years, I'm interested to ...
776 views

191 views

Dawid Skene model for BUGS

I'm a beginner in BUGS. I'm trying to code the Dawid Skene model in BUGS. The model is as follows: Currently, I'm adapting the code from Stan, here. Here is the code: ...
600 views

Longitudinal data format in WinBUGS or OpenBUGS, different number of items per time point

I am working with longitudinal data, where there are a different number of "items" per time point. I am working with the MCMCdynamicIRT1d function in ...
223 views

WinBUGS multinomial all parameters are random variables

everyone here. I want to use multinomial distribution, but p[] and N are all random. model is correct and data loaded , model compilied, but it can't still run , it says:value of binomial f must be ...
804 views

Zero trick in WinBUGS for truncation

I am using the Zero-trick to create a prior for correlation parameter. Data y is a bi-variate normal with covariance matrix with same diagonal elements and ...
230 views

How are deterministic/logical nodes represented mathematically in directed graphical models?

Various software for performing inference on graphical models support logical(a.k.a deterministic) nodes. PyMc, Winbugs, Smile are the ones I'm aware of. Based on the different inference methods ...