### Bug fixes

Hey guys: a couple of bug fixes. First of all, there was a mistake in my "outline" of the metropolis code. I had the inequality for the acceptance ratio logic going the wrong direction. The corrected code follows:

## Sample Metropolis-Hastings algorithm # function to compute log(h(theta)) log.h <- function(theta,data){} met <- function(data,initials,NREP){ # Constants n <- dim(data)[1] p <- length(initials) # Empty matrix to hold samples chain <- matrix(NA,NREP+1,p) # Initialize the chain chain[1,] <- initials for (i in 2:(NREP+1)){ # Parameters of the proposal meen <- var <- # Draw a proposal value thetastar <- rnorm(1,meen, var) # Compute the rejection ratio logr <- log.h(thetastar) + dnorm(chain[i-1,],meen,sqrt(var),log=T) - log.h(chain[i-1,]) - dnorm(thetastar,meen,sqrt(var),log=T) # Decide whether to accept or reject if (logr > 0){ chain[i,] <- thetastar } elseif (logr > log(runif(1))) { chain[i,] <- thetastar } else { chain[i,] <- chain[i-1,] } } return(chain[-1,]) }

Second, it appears that in the GeoBugs extra credit opportunity, the maps aren't going to load in because it doesn't like negative x values. One solution is to simply add a large constant to all of the longitude values in the polygon file produced by R so that they are positive.