Dear list members
I am attempting a latent variable analysis of ordered categorical response
data. My model compiles but when running it falls into the "undefined real
result" trap every few thousand replicates. The error can be provoked by
the simplified version of my model, with a single covariate and small
contrived data set, that I have included below. If anyone can tell me what
I'm doing wrong I would be most grateful.
cheers
Michael
model {
cutpoint[1] ~ dnorm(0, 0.001)I(,cutpoint[2])
cutpoint[2] ~ dnorm(0, 0.001)I(cutpoint[1],)
for ( i in 1:N ) {
mu[i] <- beta * x[i]
for ( j in 1:(Nclasses-1) ) {
logit(P[i,j]) <- cutpoint[j] - mu[i]
}
}
beta ~ dnorm(0, 0.001)
for ( i in 1:N ) {
p[i,1] <- P[i,1]
p[i,2] <- P[i,2] - P[i,1]
p[i,3] <- 1 - P[i,2]
y[i] ~ dcat(p[i,])
}
}
#inits
list(cutpoint=c(5,8), beta=1)
#data
list(N=15, Nclasses=3)
y[] x[]
1 16
1 7
1 13
1 9
1 11
2 3
2 2
2 7
2 4
2 1
3 21
3 17
3 14
3 21
3 22
END
---
Michael Bedward
Biodiversity Research & Management
Policy and Science Division
Dept. Environment and Conservation
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ph: 61-(0)2-95856493 fax: 61-(0)2-95856606
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