[Bugs-r-devel] R2WinBUGS bug fix

[Dawn W. <dwo...@in...>]

I found a bug in R2WinBUGS, which can be reproduced using the code =
below.  As
a fix, I propose removing a single line of code in bugs.sims:

  sims <- sims [sample(n.sims),]    # scramble (for convenience in =
analysis)

This line of code scrambles the samples for each parameter.  What is the
reason for doing this?  For some reason, when sims is a matrix with a =
single
column (when the user has requested that only one parameter be returned) =
this
line changes sims from a matrix object to a vector object. =20

Thank you,
Dawn



model.file <- function(){
	   for (j in 1:J){
         y[j] ~ dnorm (theta[j], tau.y[j])
         theta[j] ~ dnorm (mu.theta, tau.theta)
         tau.y[j] <- pow(sigma.y[j], -2)
       }
       mu.theta ~ dnorm (0.0, 1.0E-6)
       tau.theta <- pow(sigma.theta, -2)
       sigma.theta ~ dunif (0, 1000)
}


# Some example data (see ?schools for details):
data(schools)

J <- nrow(schools)
y <- schools$estimate
sigma.y <- schools$sd
data <- list ("J", "y", "sigma.y")
inits <- function(){
    list(theta=3Drnorm(J, 0, 100), mu.theta=3Drnorm(1, 0, 100),
         sigma.theta=3Drunif(1, 0, 100))
}
## or alternatively something like:
# inits <- list(
#   list(theta=3Drnorm(J, 0, 90), mu.theta=3Drnorm(1, 0, 90),
#        sigma.theta=3Drunif(1, 0, 90)),
#   list(theta=3Drnorm(J, 0, 100), mu.theta=3Drnorm(1, 0, 100),
#        sigma.theta=3Drunif(1, 0, 100))
#   list(theta=3Drnorm(J, 0, 110), mu.theta=3Drnorm(1, 0, 110),
#        sigma.theta=3Drunif(1, 0, 110)))

parameters <- c("mu.theta")

## Not run:=20
## You may need to edit "bugs.directory",
## also you need write access in the working directory:
schools.sim <- bugs(data, inits, parameters, model.file,
    n.chains=3D1, n.iter=3D5000,
    bugs.directory=3D"c:/Program Files/WinBUGS14/",
    working.directory=3DNULL, clearWD=3DTRUE, DIC =3D F)
print(schools.sim)