fracs.jags

model {
#  fracs[1:10] ~ ddirch(alpha[1:10])

#  for (k in 1:10) {
#    fracs[k] <- delta[k]/sum(delta[1:10]);
#    delta[k] ~ dgamma(alpha[k], 1)
#  }

  a2[1] <- sum(alpha[2:10]);
  fracs[1] ~ dbeta(alpha[1], a2[1]);
  for (j in 2:9) {
    a2[j] <- sum(alpha[(j+1):10]);
    psi[j] ~ dbeta(alpha[j], a2[j]);
    fracs[j] <- psi[j] * (1 - sum(fracs[1:(j-1)]));
  }
  fracs[10] <- 1 - sum(fracs[1:9]);


  for (i in 1:N) {
    mu[i] <- inprod(fracs[1:10], ratio[i,1:10]);
    snpA[i] ~ dbin(mu[i], total[i]);
  }
}

fracs2.jags

model {
#  fracs[1:10] ~ ddirch(alpha[1:10])

#  for (k in 1:10) {
#    fracs[k] <- delta[k]/sum(delta[1:10]);
#    delta[k] ~ dgamma(alpha[k], 1)
#  }

  a2[1] <- sum(alpha[2:10]);
  fracs[1] ~ dbeta(alpha[1], a2[1]);
  for (j in 2:9) {
    a2[j] <- sum(alpha[(j+1):10]);
    psi[j] ~ dbeta(alpha[j], a2[j]);
    fracs[j] <- psi[j] * (1 - sum(fracs[1:(j-1)]));
  }
  fracs[10] <- 1 - sum(fracs[1:9]);


  for (i in 1:N) {
    for (j in 1:10) {
      gtA[i,j] ~ dcat(prob[i,j,1:3])
      ratio[i,j] <- encoding[gtA[i,j]];
    }
    # mu[i] <- inprod(fracs[1:10], ratio[i,1:10]);
    mu[i] <- fracs[1]*ratio[i,1] + fracs[2]*ratio[i,2] + ...;
    snpA[i] ~ dbin(mu[i], total[i]);
  }
}