WinBUGS: Multiple definitions of a node

Question

I want to define the local level model in Winbugs. The model is syntactically correct. But when I run, I got this error: "multiple definitions of node y[1]"

    model {

        for (i in 1:T)
            {epsilon[i]~dnorm(0,h)
                u[i]~dnorm(0,eta_h)}    

        a[1]<-a1    
        for (j in 2:T)
            {a[j]<-a[j-1]+u[j]}

        for (k in 1:T)
            {y[k]<-a[k]+epsilon[k]}

    h~dgamma(0.0001,0.0001)
    eta~dgamma(0.0001,0.0005)
    eta_h<-eta*h

    }

    data list(T=10, a1=0.001)
    y[]
    -0.7224571
    -0.397027213
    3.1808741
    1.952424816
    4.921476096
    5.258244747
    4.383846014
    6.055572232
    5.474320734
    0.703784047
    END

Can you please tell me why and how to solve this? I've searched around on the error but each has their own specific case and there's not a generic solution or explanation as to why this arises.

jaradniemi jaradniemi · Accepted Answer · 2015-05-30T15:04:08

There is a generic solution, namely "you've defined y[1] at least twice."

In this case, you have defined it once in your data and also in the line

y[k] <- ...

WinBUGS: Multiple definitions of a node

1 Answers