hadley/ggplot2 — comment on commit 4203f765752adf31a58b5931edaa2d6cc2e2ac51
File: R/geom-path-.r line 39
By kohske:

I think the change in https://github.com/hadley/ggplot2/commit/c296b7aad5a45179f906eeb5ffe58555a0ca1353 introduced this bug.
This commit introduce the `paste` as a grouping variable.
I cannot make sure easily, since the commit cannot work due to the problem in library dependency (probably using old version of plyr or other packages).

But in my view, the code here can be improved to handle correctly the grouping variable.