geom_density() as filled area chart

[cpsievert]

To me, geom_density() should translate to a filled area chart. Right now it's translated to a histogram (with autobinning). As a result, most arguments to stat_density() are ignored and geom_density() + geom_histogram() doesn't seem to make sense. Consider the following:

p <- ggplot(mtcars, aes(wt)) + geom_density() + geom_histogram(aes(y = ..density..))

This actually gives me an error:

ggplotly(p)
Error in if (is.character(new.mode) && !is.na(new.mode)) { : 
  missing value where TRUE/FALSE needed

Any thoughts/objections @tdhock @chriddyp @mkcor?

[tdhock]

seems fine with me .. are there any tests that would need to be changed?

[cpsievert]

Yea, test-ggplot-density.R would have to change.