model {
## attempt to model weeds data using JAGS/BUGS
  b1<-exp(logb1)
  b2<-exp(logb2)
  b3<-exp(logb3)
  sigma<-exp(logsigma)
  for (i in 1:N) {
    yhat[i] <- b1/(1+b2*exp(-b3*t[i]))
    y[i] ~ dnorm(yhat[i],tau)
  }
  tau <- 1/(sigma*sigma)
  ## priors -- note must include 0 because of one chain
  logb1 ~ dunif(-10,10)
  logb2 ~ dunif(-10,10)
  logb3 ~ dunif(-10,10)
  logsigma ~ dunif(-10,10) 
}