Expanding the range of potential sizes for geoms, specifically `geom_point()`?

[dinosquash]

What is the lower bound for the size argument of various geoms, for example geom_point(), and is that controlled internal to the package?

If so, is that something that can be changed via an extension or within the function?

Motivation:

I am trying to draw very, very small points. The smallest available sizes, which seem to be in [0.0001, 0.001], are still too large for my uses.

A simple reprex that helped me identify:

df1 <- data.frame(x = seq(1, 5, 1),
                   y = rep(0, 5),
                   size = c(1, 0.1, 0.001, 0.0001, 0.00001))

chart <- ggplot() + 
  geom_point(data = df1, aes(x = x, y = y, size = size),
             stroke = 0) + 
  geom_point(aes(x = 3, y = 1), stroke = 0, shape = ".")

Even if I was satisfied with the square shape of shape = ".", the length across the square is greater than my desired diameter for a point.

Yes, I know it's small. And yes, I need it to be smaller.

[teunbrand]

The smallest size is 0. I'm unsure about the smallest non-zero size, but that'd be controlled by grid::pointsGrob() so not under ggplot2's direct control. If you find a way to draw smaller points, you can theoretically put that in an extension.

A second thing to consider is that at that size, the device is going to matter. If you're drawing sub-pixel size points, the anti-aliasing settings of raster devices are going to matter for e.g. png files. If you're using vector graphics, the smallest representable number / numeric precision in such graphics is going to matter for e.g. svg files.

It may help you to know what you can set the size range in the scale and you can include 0. Just setting a size mapping in aes() does not guarantee a particular size range.

library(ggplot2)

# I included 0 for comparison
df1 <- data.frame(x = seq(1, 6, 1),
                  y = rep(0, 6),
                  size = c(1, 0.1, 0.001, 0.0001, 0.00001, 0))

ggplot() + 
  geom_point(data = df1, aes(x = x, y = y, size = size),
             stroke = 0) + 
  geom_point(aes(x = 3, y = 1), stroke = 0, shape = ".") +
  scale_size_continuous(range = c(0, 6))

^{Created on 2025-02-19 with reprex v2.1.1}

In any case, there isn't anything for ggplot2 to do here, as the finer points of graphics are controlled by grid and graphics devices, so I'll go ahead and close this issue.