I blogged earlier (http://socialdatablog.com/what-is-wrong-with-this-graph) about the well-known risks of implying a continuous data scale in a graph where there isn't one. I just produced this alternative in the form of a heatmap table, i.e. a heatmap in which the numbers themselves are also shown. Perhaps not quite as intuitive but less misleading. It uses the cellnote facility in the heatmap2 function from the gplots package (http://cran.r-project.org/package=gplots). (This table isn't quite the same as the graph as there are two additional comparison datasets).By the way, this site is now being syndicated on r-bloggers.com.