modal.value = function (x, na.rm) 
{
    xtab <- table(x)
    xmode <- names(which(xtab == max(xtab)))
    if (length(xmode) > 1) 
        warning("There is more than one modal value!")
    return(ifelse(is.numeric(x), as.numeric(xmode), as.character(x.mode)))
}