hadley/ggplot2 — comment on commit 173094a923eb2ece8c57887755eca4e45df7b67d
File: R/geom-dotplot.r line 26
By wch:

I think you're right about the source of the problem. I don't know offhand if giving x a default value would have any negative consequences. If you want to give it a shot, first run the battery of tests in `inst/tests/visual-dotplot.r` and save them to PDF or PNGs. Then make the change, re-run the tests, and compare to see if there are any differences. If it all checks out, it would be a good idea to add another test that checks the case where `binaxis="y"` and no `x` mapping is specified.