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Reproducibility

Now that you've completed (and passed!) some Markov chain diagnostics, you're ready to finalize your RJAGS simulation. To this end, reproducibility is crucial. To obtain reproducible simulation output, you must set the seed of the RJAGS random number generator. This works differently than in base R. Instead of using set.seed(), you will specify a starting seed using inits = list(.RNG.name = "base::Wichmann-Hill", .RNG.seed = ___) when you compile your model.

This is a part of the course

“Bayesian Modeling with RJAGS”

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Exercise instructions

  • Run the provided code a few times. Notice that the summary() statistics change each time.

  • For reproducible results, supply the random number generator inits to jags.model(). Specify a starting seed of 1989.

  • Run the new code a few times. Notice that the summary() statistics do NOT change!

Hands-on interactive exercise

Have a go at this exercise by completing this sample code.

# COMPILE the model
sleep_jags <- jags.model(textConnection(sleep_model), data = list(Y = sleep_study$diff_3)) 

# SIMULATE the posterior    
sleep_sim <- coda.samples(model = sleep_jags, variable.names = c("m", "s"), n.iter = 10000)

# Summarize the m and s chains of sleep_sim
summary(sleep_sim)
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This exercise is part of the course

Bayesian Modeling with RJAGS

AdvancedSkill Level
4.7+
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In this course, you'll learn how to implement more advanced Bayesian models using RJAGS.

The two-parameter Normal-Normal Bayesian model provides a simple foundation for Normal regression models. In this chapter, you will engineer the Normal-Normal and define, compile, and simulate this model using rjags. You will also explore the magic of the Markov chain mechanics behind rjags simulation.

Exercise 1: The Normal-Normal modelExercise 2: Normal-Normal priorsExercise 3: Sleep study dataExercise 4: Insights from the prior and dataExercise 5: Simulating the Normal-Normal in RJAGSExercise 6: Define, compile, & simulate the Normal-NormalExercise 7: Posterior insights on sleep deprivationExercise 8: Markov chainsExercise 9: Storing Markov chainsExercise 10: Markov chain trace plotsExercise 11: Markov chain density plotsExercise 12: Markov chain diagnostics & reproducibilityExercise 13: Multiple chainsExercise 14: Naive standard errorsExercise 15: Reproducibility

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