如何使用R中的数据值或百分比标记直方图条

I'd like to label each bar of a histogram with either the number of counts in that bin or the percent of total counts that are in that bin. I'm sure there must be a way to do this, but I haven't been able to find it. This page has a couple of pictures of SAS histograms that do basically what I'm trying to do (but the site doesn't seem to have R versions): I'd like to label each bar of a histogram with