geom_point(): when stroke=NA, cannot change size of the point

[themeo]

I'm trying to generate a plot with points with no border displayed, just fill and to be able to change their size. However, once stroke=NA, I cannot change the size of the points.

library(ggplot2)

df = data.frame(x=rnorm(100), y=rnorm(100))
ggplot(df, aes(x, y)) + geom_point(shape=21, stroke=NA, fill="black", size=5)

ggplot(df, aes(x, y)) + geom_point(shape=21, stroke=NA, fill="black", size=0.5)

^{Created on 2021-09-20 by the reprex package (v2.0.1)}

[yutannihilation]

Thanks, confirmed. Here's another version of the reprex. Curious...

library(ggplot2)

df = data.frame(x = rnorm(100), y = rnorm(100))

f <- function(stroke) {
  ggplot(df, aes(x, y)) +
    geom_point(shape = 21, stroke = stroke, colour = "red", fill = "black", size = 50) +
    ggtitle(paste("stroke:", rlang::as_label(stroke)))
}

patchwork::wrap_plots(f(1), f(NA))

^{Created on 2021-09-20 by the reprex package (v2.0.1)}

[clauswilke]

I think it's this line:

ggplot2/R/geom-point.r

Line 133 in 759c63c

fontsize = coords$size * .pt + coords$stroke * .stroke / 2,

The NA poisons the calculation. I would always set stroke = 0 to get rid of the stroke, rather than stroke = NA.

library(ggplot2)

size <- 20
stroke <- 0
size * .pt + stroke * .stroke / 2
#> [1] 56.90551

stroke <- NA
size * .pt + stroke * .stroke / 2
#> [1] NA

^{Created on 2021-09-20 by the reprex package (v2.0.0)}

[themeo]

The reason why I set stroke = NA was that stroke = 0 does not eliminate the border:

library(ggplot2)
df = data.frame(x=rnorm(100), y=rnorm(100))
ggplot2::ggplot(df, aes(x, y)) + geom_point(shape=21, stroke=0, fill="orange", color="blue", size=3)

^{Created on 2021-09-20 by the reprex package (v2.0.1)}

[clauswilke]

Ah, apparently graphics devices interpret 0 as "smallest possible visible line thickness". You can always set the color to transparent though, to get rid of the stroke entirely.

library(ggplot2)
df <- data.frame(
  x=rnorm(100), y=rnorm(100)
)

ggplot(df, aes(x, y)) + 
  geom_point(
    shape=21, stroke=0, fill="orange",
    color="transparent", size=3
  )

^{Created on 2021-09-20 by the reprex package (v2.0.0)}

[yutannihilation]

Thanks. So, I guess the line should be something like

stroke <- coords$stroke
stroke[is.na(stroke)] <- 0
...
  fontsize = coords$size * .pt + stroke * .stroke / 2, 

[clauswilke]

Not sure entirely. That would still leave the thin outline, but getting rid of it is kind of tricky (we can't just set color = "transparent", as that will make points disappear for most point shapes). So maybe this is the way to go.

[thomasp85]

We just need to ignore stroke in the size calculations if it is NA

stroke_size <- coords$stroke
stroke_size[is.na(stroke_size)] <- 0
...
  fontsize = coords$size * .pt + stroke_size * .stroke / 2, 
  lwd = coords$stroke * .stroke / 2

Or am I missing something?

(and an aside, yes - the specs for graphics devices is that a line width of 0 should equate to the thinnest possible line, for whatever reason someone thought that was a good idea)