Question

我对贝叶斯统计数据相对较新，并尝试在某些树木放养密度数据上使用R2winBUGS应用非线性层次模型。我希望有人能帮我找到R2winBUGS给我以下错误的原因：

gen.inits无法执行（灰显）

即使我收到此错误，代码仍然会产生输出。对于收敛的参数，模型产生看似合理的输出但是当我使用两个链时，有两个参数（下面代码中的mean_N0 sigma_N0）不能很好地混合（不收敛）。链似乎从初始值开始（即mean_N0从4800.5和4799.5开始，而sigma_N0从800.5和799.5开始），但不要远离这些值。两个参数的平均值与初始设定值相差约0.5。我不确定上述错误是否导致了这种收敛问题我已经用尽了对这个问题的调查，现在我希望有人能够在下面的winBUGS或R代码中看到导致我问题的原因。如果你能提供帮助，我将非常感谢你的时间。亲切的问候 DOM

WINBUGS CODE

model {
## loop over data for likelihood 
for(i in 1:Ntotal){
  N[i] <- log(N0[P_ID_Bug[i]] - 25)-(Age[i]/(Beta_0 + Beta_1*Age[i]))  
  Y[i] ~ dnorm(N[i],tauY)
}
tauY ~ dgamma(1.0E-3, 1.0E-3)
Beta_0 ~ dnorm(9,0.25)
Beta_1 ~ dnorm(0.16,400)

## hierarchical model for each Plots intercept & slope
for (p in 1:P_ID_Length) {
    N0[p] ~ dgamma(r_N0, lambda_N0)
} 
mean_N0 ~ dnorm(5000,1.0E-6)
sigma_N0 ~ dnorm(5000,0.25E-6)
lambda_N0 <- mean_N0/(sigma_N0*sigma_N0)
r_N0 <- mean_N0 * lambda_N0
}

R CODE

data <- list(P_ID_Length = length(P_ID),
         P_ID_Bug = P_ID_Bug,
         Age=Grouped_SDen$Age, 
         Y =Grouped_SDen$LogSDen_Ha,   
         Ntotal=nrow(Grouped_SDen))

inits1 <- list(N0= rep(coef(NLS_SDen_Log_1)[[1]], P_ID_Length), 
 Beta_0 = coef(NLS_SDen_Log_1)[[2]], 
 Beta_1 = coef(NLS_SDen_Log_1)[[3]],
 tauY = 20,
 mean_N0 = 4800,
 sigma_N0 = 800
)

inits2 <- list(N0= rep(coef(NLS_SDen_Log_1)[[1]], P_ID_Length), 
 Beta_0 = coef(NLS_SDen_Log_1)[[2]], 
 Beta_1 = coef(NLS_SDen_Log_1)[[3]],
 tauY = 20,
 mean_N0 = 4800,
 sigma_N0 = 800
 )
inits <- list(inits1, inits2)
parameters <- c("N0", "Beta_0", "Beta_1", "tauY", "mean_N0", "sigma_N0")
sims <- bugs(model.file= "C:/WS/Post-Doc/TINNR/PAPER_4_WinBugs/Stocking_Growth.bug",
         data = data,
         parameters = parameters,
         inits = inits,
         n.chains = 2,
         n.iter = 1000, 
         n.burnin = 500, 
         n.thin = 2,
         debug=TRUE,
         bugs.directory = "C:/Program Files/WinBUGS14/")

我也试过使用以下格式：

inits <- function(){
  list(N0= rep(coef(NLS_SDen_Log_1)[[1]], P_ID_Length), 
   Beta_0 = coef(NLS_SDen_Log_1)[[2]], 
   tauY = 1,
   mean_N0 = 4800,
   sigma_N0 = 800
   ) 
}

请注意，第一个和第二个是相同的，下面我将向您展示第二个列表的外观。再次感谢您抽出时间寻求帮助。

[[2]]
[[2]]$N0
  [1] 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531
 [13] 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531
 [25] 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531
 [37] 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531
 [49] 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531
 [61] 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531
 [73] 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531
 [85] 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531
 [97] 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531 4920.531

[[2]]$Beta_0
[1] 8.710965

[[2]]$Beta_1
[1] 0.1623536

[[2]]$tauY
[1] 20

[[2]]$mean_N0
[1] 4800

[[2]]$sigma_N0
[1] 800

使用R2winBUGS的非线性分层模型的gen.inits错误

0 个答案: