Violin plots with too few observations are broken

[paleolimbot]

The revdep checks (#3303) identified an issue where geom_violin() plots with too few observations now fail. In 3.1.1, these plots were rendered with no geometry and no warning. This differs from the behaviour of geom_density(), which issues a warning before dropping a group with too few observations.

library(ggplot2)
ggplot(data.frame(y = 1), aes(factor(1), y = y)) + geom_violin()
#> Warning in max(data$density): no non-missing arguments to max; returning -
#> Inf
#> Error: Elements must equal the number of rows or 1

[clauswilke]

This is what I get with #3320. Is this acceptable behavior?

library(ggplot2)
ggplot(data.frame(y = 1), aes(factor(1), y = y)) + geom_violin()
#> Warning in max(data$density): no non-missing arguments to max; returning -
#> Inf

^{Created on 2019-05-08 by the reprex package (v0.2.1)}

[paleolimbot]

I can confirm that this was the behaviour in 3.1.1

[tfettrow]

I am using ggplot2 3.2.0 and am experiencing this issue again. It is not clear form the above comments whether the function just requires more data to plot properly. Any thoughts?

[lock]

This old issue has been automatically locked. If you believe you have found a related problem, please file a new issue (with reprex) and link to this issue. https://reprex.tidyverse.org/