image ()

I've a question regarding the image function, which I use frequently and
for various purposes. Apparently, the S and the R version of the image
function don't behave the same way. I've attached below a function that
under S produces regular chessboard-like figures, while it produces irregular
pattern with R (never mind different colours in R and S, this is not a
point). Does anybody know how can one obtain the chessboard images (squares
or rectangles of the same size) with R?

Best regards

Zivan


test.image <- function(n)
{
if(n < 2)
	stop("n must be >= 2")
pause <- function(msg = 
	"Press <ENTER> to continue...")
{
	cat(msg)
	readline()
	invisible()
}
for(i in 2:n) {
	i1 <- i + 1
	i2 <- i * i
	image(x = 1:i1, y = 1:i1, z = matrix(
		1:i2, ncol = i))
	pause()
}
invisible()
}