如何从mcmc RJAGS中提取数据

Question

I'm running the following model where I got a measurement for each polling week. Which produce more than 100 alpha vectors for each party. May question is, how could I stockpile them in a way I could draw a line graph?

model{
  ## measurement 
 for(i in 1:NPOLLS){  
      p1[i] ~ dnorm(alpha1[WoY[i]] + pollster1[org[i]], prec1[i])
       p2[i] ~ dnorm(alpha2[WoY[i]] + pollster2[org[i]], prec2[i])
       p3[i] ~ dnorm(alpha3[WoY[i]] + pollster3[org[i]], prec3[i])

}

## transition 
for(i in 2:NPERIODS){    
    alpha1[i] ~ dnorm(alpha1[i-1],phi1)
    alpha2[i] ~ dnorm(alpha2[i-1],phi2)
    alpha3[i] ~ dnorm(alpha3[i-1],phi3)
 }

pollster1[1] <- -sum(pollster1[2:NPOLLSTERS])
pollster2[1] <- -sum(pollster2[2:NPOLLSTERS])
pollster3[1] <- -sum(pollster3[2:NPOLLSTERS])

## priors
phi1 ~ dgamma(5000,1)     
alpha1[1] ~ dunif(.2,.4) 
phi2 ~ dgamma(5000,1)     
alpha2[1] ~ dunif(.2,.4)
phi3 ~ dgamma(10000,1)     
alpha3[1] ~ dunif(.1,.3)
    for(i in 2:NPOLLSTERS){
    pollster1[i] ~ dnorm(0,.01);    
    pollster2[i] ~ dnorm(0,.01);
    pollster3[i] ~ dnorm(0,.01);
 } }

Answer 1

jags function provid a mmcm.list object with a summary generic function for this class of object. Use str and name functions on your new object return by the jags function and you need to find something like mcmc . The mcmc sub-object is a matrix of class mcmc.list containing the posteriors with n row the number of iterartion and n col the estimated parameters. So you can extract what you want. The length of the mcmc object is equal to the number of chains. They also have a generic plot.mcmmc funcion to draw the posterior density.