bv <- function(x,ab,nbin,eye=c(-6,-8,5),opt=F) {

if(nbin[1]<=0|nbin[2]<=0) stop("Number of bins along x or y axis nonpositive")
if(ab[1,1]>=ab[1,2] | ab[2,1]>=ab[2,2])
	stop("Array ab contains intervals with negative orientation")
if (ncol(x) != 2 ) stop("Data matrix does not have exactly 2 columns")

s3 <- sqrt(3.)
par(usr=c(-s3,s3,-s3,s3))

	nc <- integer(nbin[1]*nbin[2])
	nf <- c(5,3,5*nbin[1]*nbin[2])
	face <- single(nf[1]*nf[2]*nf[3])
	out  <- single(nf[1]*nf[2]*nf[3])
	idir <- integer(5*nbin[1]*nbin[2])
	tx <- single(nbin[1]+1)
	ty <- single(nbin[2]+1)
	dist <- single(nf[3])
	iptr <- integer(nf[3])
	square <- single(4*nf[3])

	z <- .Fortran("bv",
	as.single(x),
	as.integer(nrow(x)),
	as.single(ab),
	as.integer(nbin),
	as.integer(nc),
	as.integer(nf),
	as.single(face),
	as.single(out),
	as.integer(idir),
	as.single(tx),
	as.single(ty),
	as.single(eye),
	as.single(dist),
	as.integer(iptr),
	as.single(square))
list(nc=nc,ab=ab)
}