that's the bvnpdf() code:
bvnpdf <- function(xy, mu, Siginv, detSig){
f<-numeric()
x <- xy[[1]]
if(xy[[1]]>xy[[2]] & (1==2)) {
f <- 0} else {
v <- rbind(xy[1], xy[2])
e <- t(v-mu) %*% Siginv %*% (v-mu)
f <- as.numeric(exp(-e/2)/(2*pi)/sqrt(detSig))
}
f
}