color.scale <- function(z, col = tim.colors(256), 
    zlim = NULL, transparent.color = "white", eps = 1e-08) {
    #
    # converts real values to a color scale of NC values.
    # role of eps is to prevent values exactly at the end of the range from being
    # missed
    if (is.null(zlim)) {
        zlim <- range(z, na.rm = TRUE)
    }
    z[(z < zlim[1]) | (z > zlim[2])] <- NA
    NC <- length(col)
    breaks <- seq(zlim[1] * (1 - eps), zlim[2] * (1 + eps), , 
        NC + 1)
    # the magic of R ...
    icolor <- cut(c(z), breaks)@.Data
    # returned values is a vector of character hex strings encoding the colors.
    ifelse(is.na(icolor), transparent.color, col[icolor])
}