title: ggplot2 stacked histogram - convert to density plot
body: <p>I can easily make a stacked histogram using ggplot2 with counts on the y-axis. What I want is to convert this plot in terms of density. I can do this by adding the aes(y=..density..) into the geom_histogram layer; but what ggplot does is plot the density of each individual data series to have a total area of 1 each. So if you are stacking 4 data series in one histogram the total area of the bars will be 4.</p>
  
  <p>What I am after is to plot the stacked histogram in terms of density but to have all of the data series considered in calculating the density. In other words... I want the density stacked histogram to have the same proportion bars as the counts histogram. </p>