Piechart in R, borders too pointy on the inside

Question

I'm making a piechart using ggplot2 and it looks fine in RStudio:

data <- data.frame(
  continent=c("Europe", "N. America", "S. America", "Asia", "Africa", "Australia"),
  value=c(80, 30, 20, 110, 40, 5)
)

library(ggplot2)
ggplot(data, aes(x="", y=value, fill=continent)) +
  geom_bar(stat="identity", width=1, color="black")+
  coord_polar("y") +
  theme_void() 
ggsave("piechart.png")

However, when I open the saved picture, you can see that the center has an unwanted spike from the green segment:

I feel this looks rather bad. Can I remove it somehow? Maybe change the line thickness so this is not as pronounced?

I am no {ggplot2} expert. Is it due to the size you use to save the plot? Have you played around around with the size arguments in ggsave? (On my machine) it defaults to > ggsave("piechart.png") Saving 8.85 x 4.46 in image. — Friede
– Friede, Commented Aug 28, 2024 at 8:19
I've tried using different sizes, and larger sizes do help a little. But it's mainly because the pointy spike seems proportionally smaller. I'd like to avoid the problem altogether, since it seems the lines are drawn longer than they need to be. — mkranj
– mkranj, Commented Aug 28, 2024 at 8:27
If you set the width to default 0.9, there is no issue, why are we setting it to 1? — zx8754
– zx8754, Commented Aug 28, 2024 at 8:58

I_O · Accepted Answer · 2024-08-28 09:19:27Z

3

Edit

Setting the linejoin to 'bevel' helps w/o fiddling around with inner radius as in previous approach:

library(ggplot2)
ggplot(data, aes(x="", y=value, fill=continent)) +
  geom_bar(stat="identity", width=1, color="black",
           linejoin = 'bevel'
           )+
  coord_polar("y") +
  theme_void()

You could use coord_radial instead of coord_polar, prevent axis expansion and set a minute inner radius:


    ggplot(data, aes(x="", y=value, fill=continent)) +
      geom_bar(stat="identity", width=1, color="black")+
      coord_radial('y', expand = FALSE, inner.radius = 0.01) +
      theme_void()

edited Aug 28, 2024 at 9:19

answered Aug 28, 2024 at 8:33

I_O

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3 Comments

zx8754 Over a year ago

You still have the green bar edge issue there.

I_O Over a year ago

Thank you. The inner radius needs some trial & error to maneuvre between spike and hole.

mkranj Over a year ago

Thank you, using "bevel" works beautifully!

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