treemap package is probably the best way to build treemaps in R. The 3 examples below will teach you how to build a very basic treemap, how to deal with subgroups, and how to customize the figure. Note that once you master this package, you can very easily build an interactive version as described below.
Most basic treemap
Start with the most basic treemap you can build. No customization, no subgroups, easy code.
d3treeR allows to build interactive treemaps with
R. Click on a group to zoom in and reveal subgroups. Click on the group name on top to unzoom and come back to the previous state. Note that the syntax used in previous charts above is exactly the same. Only one more line of code is needed, give it a go!