dotchart.with.add <- function (x, labels = NULL, groups = NULL, gdata = NULL, cex = par("cex"), 
    pch = 21, gpch = 21, bg = par("bg"), color = par("fg"), gcolor = par("fg"), 
    lcolor = "gray", xlim = range(x[is.finite(x)]), main = NULL, 
    xlab = NULL, ylab = NULL, add = F, ...) 
{
    opar <- par("mai", "mar", "cex", "yaxs")
    on.exit(par(opar))
    par(cex = cex, yaxs = "i")
    if (!is.numeric(x)) 
        stop("'x' must be a numeric vector or matrix")
    n <- length(x)
    if (is.matrix(x)) {
        if (is.null(labels)) 
            labels <- rownames(x)
        if (is.null(labels)) 
            labels <- as.character(1L:nrow(x))
        labels <- rep(labels, length.out = n)
        if (is.null(groups)) 
            groups <- col(x, as.factor = TRUE)
        glabels <- levels(groups)
    }
    else {
        if (is.null(labels)) 
            labels <- names(x)
        glabels <- if (!is.null(groups)) 
            levels(groups)
        if (!is.vector(x)) {
            warning("'x' is neither a vector nor a matrix: using as.numeric(x)")
            x <- as.numeric(x)
        }
    }
if(!add)    plot.new()
    linch <- if (!is.null(labels)) 
        max(strwidth(labels, "inch"), na.rm = TRUE)
    else 0
    if (is.null(glabels)) {
        ginch <- 0
        goffset <- 0
    }
    else {
        ginch <- max(strwidth(glabels, "inch"), na.rm = TRUE)
        goffset <- 0.4
    }
    if (!(is.null(labels) && is.null(glabels))) {
        nmai <- par("mai")
        nmai[2L] <- nmai[4L] + max(linch + goffset, ginch) + 
            0.1
        par(mai = nmai)
    }
    if (is.null(groups)) {
        o <- 1L:n
        y <- o
        ylim <- c(0, n + 1)
    }
    else {
        o <- sort.list(as.numeric(groups), decreasing = TRUE)
        x <- x[o]
        groups <- groups[o]
        color <- rep(color, length.out = length(groups))[o]
        lcolor <- rep(lcolor, length.out = length(groups))[o]
        offset <- cumsum(c(0, diff(as.numeric(groups)) != 0))
        y <- 1L:n + 2 * offset
        ylim <- range(0, y + 2)
    }
if(!add) plot.window(xlim = xlim, ylim = ylim, log = "")
    lheight <- par("csi")
    if (!is.null(labels)) {
        linch <- max(strwidth(labels, "inch"), na.rm = TRUE)
        loffset <- (linch + 0.1)/lheight
        labs <- labels[o]
        mtext(labs, side = 2, line = loffset, at = y, adj = 0, 
            col = color, las = 2, cex = cex, ...)
    }
    abline(h = y, lty = "dotted", col = lcolor)
    points(x, y, pch = pch, col = color, bg = bg)
    if (!is.null(groups)) {
        gpos <- rev(cumsum(rev(tapply(groups, groups, length)) + 
            2) - 1)
        ginch <- max(strwidth(glabels, "inch"), na.rm = TRUE)
        goffset <- (max(linch + 0.2, ginch, na.rm = TRUE) + 0.1)/lheight
if(!add) {
        mtext(glabels, side = 2, line = goffset, at = gpos, adj = 0, 
            col = gcolor, las = 2, cex = cex, ...)
}
        if (!is.null(gdata)) {
            abline(h = gpos, lty = "dotted")
            points(gdata, gpos, pch = gpch, col = gcolor, bg = bg, 
                ...)
        }
    }
if(!add) {
    axis(1)
    box()
    title(main = main, xlab = xlab, ylab = ylab, ...)
}
    invisible()
}



if(F) {
# use the new function as the default function:
dotchart <- dotchart.with.add

# example:
mean.values<-colMeans(VADeaths)
mean.values<-apply(VADeaths, 2, mean)
median.values<-apply(VADeaths, 2, median)

#dotchart(VADeaths, gdata=median.values)
dotchart(VADeaths, gdata=mean.values)
dotchart(VADeaths, gdata=median.values, add=T, gcol = 2, gpch = 19)

}