Extend the plot range of geom_density() nicely

[yutannihilation]

(See #3708 (comment))

Compared to the base R's density plot, geom_density() draws in a narrower range. As a result, the line doesn't touch the X-axis. Though it needs a lot of care to extrapolate the data correctly, it's nice if geom_density() can draw the bottom right one below.

plot(density(diamonds$carat, adjust = 5))

p <- ggplot(diamonds, aes(carat)) +
  geom_density(adjust = 5)

patchwork::wrap_plots(
  p + ggtitle("(default)"),
  p + ggtitle("(expanded)") + expand_limits(x = -0.5)
)

[teunbrand]

@yutannihilation Do you feel strongly that this should be a setting in geom_density()? I think expanding the limits is an adequate solution to this problem, or am I missing something?

[yutannihilation]

Hmm, thanks for pinging. Now I don't have a strong opinion. The problem I worried was simply that a different behavior than base R might be confusing to users. So, in my opinion, "hey, you can do the same thing as base R if you know how to do it!" is not the solution.

However, as I haven't seen such a complain, probably I was wrong. I'm fine to close this issue.

[teunbrand]

In the development version of ggplot2 the bounds argument can also contribute in expanding the range (probably as side-effect of #5642). This is just to say that there is some extra tooling we can use to achieve this.

devtools::load_all("~/packages/ggplot2/")
#> ℹ Loading ggplot2
ggplot(diamonds, aes(carat)) + geom_density(adjust = 5, bounds = c(-1, Inf))

^{Created on 2024-12-05 with reprex v2.1.1}

I think this falls in line with #3708 (comment) 'willful extrapolation' notion, so unless there is a strong opinion to the contrary, I'll lay this issue to rest for now.

[yutannihilation]

the bounds argument can also contribute in expanding the range (probably as side-effect of #5642).

Oh, good to know. Thanks!

I'll lay this issue to rest for now.

👍