108

When using ggplot, I can set shape to 21-25 to get shapes that have independent setting for the internal (fill) and border (col) colors, like so:

df <- data.frame(id=runif(12), x=1:12, y=runif(12))
ggplot(df, aes(x=x, y=y)) + 
  geom_point(aes(fill=id, size=id), colour="black", shape=21)

enter image description here

However, I can't figure out how to control the thickness of the shape borders, either setting them absolutely or as an aesthetic mapping. I note that if I set an lwd value, it overrides the size aesthetic:

ggplot(df, aes(x=x, y=y)) + 
  geom_point(aes(fill=id, size=id), colour="black", shape=21, lwd=2)

enter image description here

How do I control the border thickness?

smci
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Noam Ross
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3 Answers3

154

Starting in version 2.0.0 of ggplot2, there is an argument to control point border thickness. From the NEWS.md file:

geom_point() gains a stroke aesthetic which controls the border width of shapes 21-25 (#1133, @SeySayux). size and stroke are additive so a point with size = 5 and stroke = 5 will have a diameter of 10mm. (#1142)

Thus, the correct solution to this is now:

df <- data.frame(id=runif(12), x=1:12, y=runif(12))
ggplot(df, aes(x=x, y=y)) + 
  geom_point(aes(fill=id, size=id), colour="black", shape=21, stroke = 2)

Output

Noam Ross
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    Can you add the output? – Thomas Dec 18 '15 at 18:34
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    For future compatibility and clarity it would be nice to say "Starting in version x.xx" rather than "the latest version". – Gregor Thomas Dec 18 '15 at 19:43
  • Is there a way of controlling the thickness of the stroke based on the variables? Something along the lines of "scale_stroke_manual"? – Ricecakes Sep 06 '19 at 04:12
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    As a response to my own comment above, we can use scale_discrete_manual. See link here: https://github.com/tidyverse/ggplot2/issues/3507#issuecomment-526212978 – Ricecakes Sep 06 '19 at 04:29
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    Any ideas why stroke=0 still draws it in PDF but not in PNG? – gkcn Jun 01 '21 at 21:39
19

It feels a bit hacky but you can add a "background" set of dots with the size set to the aesthetic mapping plus some small constant to enlarge the border of the dots. Play with the constant to get the desired border width.

You'll also have to disable the size legend to stop it displaying the legend on the graph...

ggplot(df, aes(x=x, y=y)) + 
  geom_point(aes(size=id+0.5), colour="black" , show_guide = FALSE )+
  scale_size( guide = "none" )+
  geom_point(aes(fill=id, size=id), colour="black", shape=21)

enter image description here

Simon O'Hanlon
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1

Another solution is to create the plot in R and then export it to a .svg file. The linewidth can then be changed using vector graphics editing software (e.g., Inkscape). This method is particularly useful when data points overlap.

Gopal Penny
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