Hi, I want to use a discrete color ramp with plot3D, and show NA values as white (default). I get unexpected results per the following. # as in help(slice3D) example: par(mfrow = c(2,2)) x <- y <- z <- seq(-1, 1, by = 0.1) grid <- mesh(x, y, z) colvar <- with(grid, x*exp(-x^2 - y^2 - z^2)) slice3D (x, y, z, colvar = colvar, theta = 60) # # use three discrete classes and colors instead of a continuous ramp slice3D(x, y, z, colvar = colvar, theta = 60, col = c("blue", "green", "red"), breaks = c(-0.5, -0.1, 0.1, 0.5)) # now set a vertical slice of the cube to NA colvar[10,,] <- NA # displays as expected; default NAcol = "white" slice3D (x, y, z, colvar = colvar, theta = 60) # does not display as expected--notice # the colors shifted down in value, with NA and -0.5 to -0.1 now both white. slice3D(x, y, z, colvar = colvar, theta = 60, col = c("blue", "green", "red"), breaks = c(-0.5, -0.1, 0.1, 0.5)) Please help. Thanks, Scott Scott Waichler, PhD Pacific Northwest National Laboratory scott.waichler at pnnl.gov Richland, Washington, USA