Stop geom_density_ridges from showing non-existent tail values

One option is to use stat_density() instead of stat_density_ridges(). There are some things that stat_density() can't do, such as drawing vertical lines or overlaying points, but on the flip side it can do some things that stat_density_ridges() can't do, such as trimming the distributions to the data ranges.

# Remove all negative values for "Minimum Temperature"
d <- lincoln_weather[lincoln_weather$`Min Temperature [F]`>=0,]

ggplot(d, aes(`Min Temperature [F]`, Month, group = Month, height = ..density..)) +
  geom_density_ridges(stat = "density", trim = TRUE)

As an alternative, you could draw a point rug, maybe that serves your purpose as well or better:

ggplot(d, aes(`Min Temperature [F]`, Month)) +
  geom_density_ridges(rel_min_height = 0.01, jittered_points = TRUE,
                      position = position_points_jitter(width = 0.5, height = 0),
                      point_shape = "|", point_size = 2,
                      alpha = 0.7)

Note: those two approaches cannot currently be combined, that would require some modifications to the stat code.

Well, turns out I should have just read the documentation more closely. The key part is:

"The ggridges package provides two main geoms, geom_ridgeline and geom_density_ridges. The former takes height values directly to draw ridgelines, and the latter first estimates data densities and then draws those using ridgelines."

There are multiple ways to handle this issue. Here is one:

ggplot(d, aes(`Min Temperature [F]`, Month, height=..density..)) +
  geom_density_ridges(stat = "binline", binwidth=1,
                      draw_baseline = F)