model {
  # prior for zygote frequencies
  for (i in 1:3) {
    xz1[i] ~ dgamma(1, 0.001)
    xz[i] <- xz1[i]/sum(xz1[])
  }
  # prior for adult frequencies
  for (i in 1:3) {
    xa1[i] ~ dgamma(1, 0.001)
    xa[i] <- xa1[i]/sum(xa1[])
  }
  # prior for p
  p ~ dunif(0,1)

  # likelihood of zygote frequencies
  nz[1:3] ~ dmulti(xz[], nzygote)
  # likelihood of adult frequencies
  na[1:3] ~ dmulti(xa[], nadult)
  # likelihood of equilibrium sample
  k ~ dbin(p, n)

  # relative fitness of A1A1
  w11 <- (xa[1]/xa[2])*(xz[2]/xz[1])
  w22 <- (xa[3]/xa[2])*(xz[2]/xz[3])
  # selection coefficients
  s1 <- 1 - w11
  s2 <- 1 - w22
  # predicted equilibrium
  # poly = 0 if s1 < 0 (monomorphism predicted)
  # poly = 1 if s1 >= 0 (polymorphism predicted)
  poly <- step(s1)
  # p.eq = s2/(s1+s2) if poly = 1 (polymorphism predicted)
  # p.eq = 1 if poly = 0 (monomorphism predicted)
  p.eq <- s2/(s1 + s2)*poly + (1-poly)
  # difference between observed and expected
  # caclculated only when polymorphism equilibrium is predicted
  diff.p <- (p.eq - p)*poly
}

# data
list(nz=c(41, 82, 27), na=c(57, 169, 29), nzygote = 150, nadult =255, k = 240, n = 300)