[R] R2WinBUGS with Multivariate Logistic Regression

[Christopher Kelvin]

Dear R-User,
I have written a simple code to analyze some data using Bayesian logistic regression via the R2WinBUGS package. The code when run in WinBUGS stops WinBUGS from running it and using the package returns no results also. 


I attach herewith, the code and a sample of the dataset.

Any suggestion will be greatly appreciated.

Chris Guure
Biostatistics Department

University of Ghana




library(R2WinBUGS)
library(coda)model1<-function(){
for (i in 1:N) {
# likelihood function
ms[i] ~ dbin( p [ i ], N )
logit(p [ i ] ) <- alpha + bage*age[ i ] + bpam*pam[i ] + bpah*pah[i] 

}
### prior for intercept
alpha ~ dnorm(0,0.0001)

# prior for slopes
bage ~ dnorm(0,0.0001)
bpam ~ dnorm(0,0.0001) 
bpah ~ dnorm(0,0.0001)


# OR for alpha
or.age<-exp(bage)
# OR for hbp
or.pam <- exp(bpam)
# OR for fdm
or.pah <- exp(bpah)

}

data=cbind(ms=c(0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0),
age=c(77, 83, 75, 78, 75, 83, 85, 80, 80, 85, 76, 77, 80, 76, 88, 77, 81, 78, 85, 81),
pam=c(0, 0, 1, 1, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1),
pah=c(1, 1, 0, 0, 1, 0, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1, 1, 1, 0, 0))
N=20

#### initial values                                                                                             ###
lineinits <- function(){
list(alpha=1,bage= 0.05, bpam=0.05, bpah=0.05)
}

## CODA output 
lineout1 <- bugs(data, lineinits, c("bage", "alpha","bpam", "bpah", "or.age", "or.pam", "or.pah"), model1,n.iter = 11000, n.burnin = 1000, n.chains = 2, codaPkg = T, DIC = TRUE) 


### Posterior summaries
line.coda <- read.bugs(lineout1) 
summary(line.coda)