Questions tagged [bugs]

BUGS is an acronym for Bayesian inference Using Gibbs Sampling; BUGS is also a software package for doing this.

2
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1answer
99 views

Bayesian p-value in wrong direction using step function in JAGS / BUGS

I have estimated a Weibull regression model in JAGS using rjags and R2JAGS. The estimated posterior predictive p-values using the step() function confuse me. They make sense (comparing them to lower ...
1
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0answers
81 views

How to specify a zero-inflated Dirichlet model in JAGS/BUGS

There was a recent publication discussing the advantages of the zero-inflated dirichlet for microbiome count data which is compositional (you are modeling a matrix of species relative abundance data ...
0
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1answer
184 views

Predict credible interval of Poisson-distributed response based on Lambda credible interval

I am approaching Bayesian inference. Could you review my steps and give me a hand with my model predictions? I am using a N-mixture model to predict how many individuals N of a rare species inhabit a ...
0
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0answers
183 views

How to obtain the posterior predictive p-value in WinBUGS

I want to assess the goodness-of-fit of a model in WinBUGS. As part of this, I want to calculate the posterior predictive p-value, which should be around 0.5 if the model is a good fit to the data. I ...
1
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1answer
24 views

Framework for simulation study to validate bayesian models

I am looking for a framework that would allow to take JAGS/bugs model and on many sets of simulated data test if there is a bias (or not) in the parameter estimates (the real parameters would be known ...
1
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0answers
75 views

Random effects in ZIP or ZINB models - count portion, Bernoulli portion, or both?

I'm building some zero-inflated models that need to include random effects, and I can't find a definitive answer for whether I should include the random effects in the part of the model that describes ...
3
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1answer
330 views

“Mixed effect” ANOVA in R with JAGS/BUGS

I would like to be able to code the following linear mixed model into a bayesian framework. In the traditional/frequentist view, the model would be coded like this: ...
1
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0answers
102 views

Standard Deviations of Random Effects

I would have a question regarding the estimates of the random effects for a model fitted with JAGS. I want to fit a mixed model of the form: $$y_{ij}=\beta_{0j}+\beta_{1j}x_{ij}+\beta_2+e_{ij}$$ $$\...
2
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0answers
140 views

Comparing the Widths of two Posterior Distributions

I have a question regarding the task of my term paper case study, which is about Bayesian multilevel modelling and I would greatly appreciate it, if you could help me out. The exact assignment reads ...
0
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1answer
234 views

Cumulative link model in JAGS or BUGS [closed]

I'm trying to implement a cumulative link model in JAGS. My outcome variable (Likert-style questionnaire) has four categories. There is currently no predictor in the model, I will add them once the ...
1
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0answers
58 views

Meaning of Intercept Parameter in a Bayesian Longitudinal HLM

I have been working through John Kruschke's excellent book on Bayesian Data Analysis but now have found myself in experimental-design territory not covered in the book: a longitudinal linear mixed-...
2
votes
1answer
95 views

Recovering noise-free variables in binary trials

I have a collection of $N$ different objects. An expert "looks" at the object $O_i$ and produces a prediction: binary label $y_i\in\{0,1\}$. The predicted binary label $y_i$ is observed (data) and is ...
0
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1answer
797 views

Bayesian estimation of Dynamic Linear Models with RStan

I'm reading the Dynamic Linear Models with R book, where most of chapter 4 is devoted to bayesian estimation of parameters. They code most of it manually though, and it seems it can get quite tricky ...
1
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1answer
607 views

Marginal prior $p(\mu)$ of mean of a normal distribution when both mean and variance are unknown

I read that if the data is normally distributed with mean $\mu$ and variance $\sigma^2$ (both unknown) then to have the joint posterior distribution $p(\mu, \sigma^2 | y)$ in closed form, one has to ...
0
votes
1answer
197 views

Hierarchical Bayesian model - issues with JAGS/BUGS switching between lognormal and normal

I'm trying to construct a hierarchical model using JAGS, but I'm running into issues converting between normal/lognormal distributions and the more I stare at my problem, the more confused I get. ...
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0answers
75 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 ...
0
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0answers
18 views

OpenBUGS intuition with data [duplicate]

I've recently discovered Bayesian statistics, currently I am experimenting with Openbugs, yet I cant grasp the concept of what happens with the inputted data. I understand mcmc, yet all of examples I'...
1
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0answers
162 views

Testing Key Assumptions of Cultural Psychology with Bayesian Analysis [closed]

I have been trying to come up with a way to represent some of the key assumptions of culture in actual measurement and statistical modeling practices. For all of these points, it seems like the ...
1
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1answer
83 views

How to include Cohen's D from Meta-Analysis into JAGS/BUGS mean difference model

I was wondering if anyone knew of a way to use Cohen's D (and Standard Error) as an informed prior while building a BUGS model (to be tested in JAGS through R) that compares the mean difference ...
0
votes
1answer
4k views

Gamma parameterization and how to randomly generate $\sigma$'s for use in `rnorm(n, $\mu$, $\sigma$)`

Say I have a normal distribution parameterized with a mean ($\mu$) and precision ($\tau = 1/\sigma^2)$. In JAGS, I would specify a prior for $\tau$ as ...
0
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1answer
103 views

Observed function of hidden random variables

Let's say a worker can perform 4 types of tasks in a day: A,B,C,D. Each of which tasks takes time that is distributed according to some probability distribution, say $$ T_A \sim Gamma(\alpha_A, \...
5
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0answers
374 views

AR(1) model - which prior to use?

I want to use the following univariate model: $y_t = \mu_t + \epsilon_t, \ \epsilon_t \sim N(0,1)$ $\mu_t = \phi \mu_{t-1} + \omega_t, \ \omega_t \sim N(0,\sigma_\omega^2)$ That is, $\mu_t$ follows ...
2
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0answers
346 views

Discrete MCMC JAGS chains get stuck

I have been running a model where one of the parameters is discrete. I can't think of a simple way to represent this model, so I won't (unless necessary) post it here. My issue is, that when I look ...
1
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2answers
332 views

JAGS choosing a random subset of a vector

I would like to allow the subset of a vector I am summing over to be a random quantity. My model is of the form (albeit more complex): ...
2
votes
1answer
725 views

Bayesian meta analysis: implementation in BUGS/JAGS/STAN

I would like to conduct a meta analysis in order to collate the information from a number of studies. The parameter of interest is a probability $\theta$. In each of the studies, the observed data $...
4
votes
1answer
787 views

Crossvalidation in hierarchical bayesian models (HBMs)

I am trying to find a way to cross-validate Hierarchical Bayesian Models used for predicting and modelling abundance in Species Distribution Models. For this purpose, I have tried posterior predictive ...
2
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2answers
621 views

Suspiciously high Multivariate PSRF from gelman.diag()

I am using "Multivariate PSRF" statistics from gelman.diag() function to analyze my MCMC chains. Now I analyzed convergence 471 variables (parameters for each site)....
1
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0answers
55 views

OpenBUGS and coda library

I've fitted a hierarchical model with OpenBUGS using R2WinBUGS package of R. Now, I'd like to use the functions contained in the ...
0
votes
2answers
760 views

Comparing a model with two rate parameters to a model with one. Conjugate priors?

I have a model which includes two exponential rate parameters. I would like to test whether a model with two individual rates describes some data better than a model for which both rates are the same. ...
7
votes
1answer
4k views

What is the difference between R hat and psrf?

In convergence diagnosis in WinBUGS/JAGS/Stan, there are different statistics reported for each variable. In WinBUGS/Stan, Rhat ($\hat{R}$) is reported. In JAGS with the ...
1
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1answer
368 views

How to define function in OpenBUGS

In my Hierarchical Bayesian Model, in the data layer y[i] <- M(t,u,v)+ N[0,sigma_y] where M is a complicated function. I have generated the output of this M by ...
6
votes
0answers
728 views

Is my OpenBUGS / WinBUGS model well specified?

I've just started trying to use OpenBUGS for Bayesian analysis of stochastic volatility models. In particular, I'm trying to calculate stochastic covariance, similar to the DC-MSV model specified by ...
1
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0answers
1k views

What is the form of link function in this BUGS multinomial regression example?

The alligators example from openbugs examples repository is the same example that comes with winbugs. Basically this is a multinomial logistic regression example in which the outcome variable has 5 ...
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0answers
121 views

Point Estimate of normally distributed threshold parameter with unknown mean and variance

I'm new to Bayesian analysis an applied what I learned in John Kruschke's book to simplified versions of a model I previously fitted with non-Bayesian methods. For those simplified versions, even ...
3
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0answers
190 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: ...
2
votes
1answer
351 views

Concern with using the DIC to compare Bayesian models

The deviance information criterion (DIC) is a very popular tool for Bayesian model selection, due, in part, to its support by the BUGS platforms. However, there are some remaining limitations as ...
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0answers
218 views

Multigroup Longitudinal Item Response WinBUGS OpenBUGS

I was able to fit the Longitudinal IRT model in Winbugs for an ordinal response by extending the BUGS code I took from the paper by Curtis in JSS http://www.jstatsoft.org/v36/c01/paper/ However, I am ...
2
votes
1answer
860 views

How to Implement an Empirical Bayes Analysis in BUGS/JAGS/Stan

My data is a set of $N$ observations $y_i$. I would like to estimate $\mu$ and $\sigma$ in the following model: $y_i \sim \mathrm{Normal}(\theta, \sigma)$ $\theta \sim \mathrm{Normal}(\mu, \frac{\...
0
votes
1answer
68 views

Linear Regression with Outlier accounting in Bugs

I'm trying to redo an exercise in BUGS from this webpage: a linear regression over a data set with some outliers, using a model that accounts for them. This model uses a mixture of signal and noise (...
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0answers
210 views

BUGS/JAGS for Nominal Response Model

I am a beginner with BUGS/JAGS and I was hoping to gather the opinion of you, experts. I am trying to implement a Nominal Item Response Analysis (Polytomous, not ordered, like a multiple-choice exam) ...
1
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0answers
166 views

number of stochastic nodes in bayesian multivariate distribution?

I'm doing some bayesian modeling using BUGS - JAGS to be specific. I find it hard to infer how many stochastic (i.e. non-deterministic) nodes there really are when I use multivariate distributions. ...
2
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0answers
53 views

BUGS with very large sample size

I posted this question on the JAGS help discussion, I was seeing if I could get any help here: I wish to fit a survival model using the data below (first two columns are time points, NA represents ...
1
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0answers
4k views

WinBUGS/OpenBUGS Gamma distribution parameters [closed]

According to the WinBUGS manual the gamma distribution is defined by: dgamma(r,mu) However, what is r? Is it the shape, scale ...
1
vote
1answer
325 views

JAGS burn-in phase takes ZERO time? [duplicate]

My breath was taken away by this. I tried to run my JAGS model with different number burn-in samples but it still takes the same amout of time!! ...
0
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0answers
52 views

Regarding three R packages for Bayesian analysis [duplicate]

There are several R packages for Bayesian analysis, i.e., RBugs, JAGS,MCMCPack. Are there ...
2
votes
0answers
152 views

Is this JAGS model ok, and can it be made faster?

I'm very new to Bayesian analysis, and I've come up with the following model. My goal is to get for each individual "test unit" a distribution that describes the lift in success rate under one of ...
5
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0answers
1k views

CAR spatial models in JAGS

WinBUGS comes with the GeoBUGS add-on, which contains a number of predefined model structures that are suitable for modelling spatial data structures e.g. geostatical structures (spatial.exp), ...
1
vote
1answer
922 views

Naive SE vs Time Series SE: which statistics should I report after Bayesian estimation?

I am new to Bayesian estimation. When I do some estimations with JAGS, I find there are statistics called Naive SE and Time Series SE. What exactly do they mean? Is it necessary that I report one or ...
7
votes
1answer
4k views

Specify a Zero-inflated (Hurdle) Gamma Model in JAGS/BUGS

I'm trying to use a zero-inflated gamma model (or a gamma 'hurdle' model). The model is a mixture of logistic regression and generalized linear modeling. I can do this analysis in two steps: 1) do a ...
11
votes
2answers
1k views

How do programs like BUGS/JAGS automatically determine conditional distributions for Gibbs sampling?

Seems like full conditionals are often quite difficult to derive, yet programs like JAGS and BUGS derive them automatically. Can someone explain how they algorithmically generate full conditionals for ...