Question

I would like to annotate a plot so as to show the totals for each column. For example

 ggplot(diamonds, aes(clarity, fill=cut)) + 
        geom_bar(position="fill") +
        scale_y_continuous(name="proportion")

This will produce a stacked barplot. However it is difficult to know what is n for each of the bars. I1,SI2 and so on. How can I annotate it so that, for each bar, n is displayed at the top?

Answer 1

The easiest way is to compute the totals before plotting, then adding them to the plot separately. First, we calculate columns totals:

totals = tapply(diamonds$price, diamonds$clarity, length)
dd = data.frame(clarity = names(totals), labels = as.vector(totals), y= 1)

Then we use geom_text to add the totals:

ggplot(diamonds, aes(clarity)) + 
    geom_bar(aes( fill=cut), position="fill") +
    scale_y_continuous(name="proportion") + 
    geom_text(data=dd, aes(x=clarity, y=y, label=labels), size=4)