Axis ticks reserve space, even when absent

[teunbrand]

Hi there,

I've come across a few cases on SO where some confusion was created by axis ticks creating whitespace around the plot, even when axis.ticks = element_blank() (example 1, example 2). I'm not sure whether this is intentional or not, but I found it to be a bit counterintuitive. To illustrate:

library(ggplot2)

p <- ggplot(mpg, aes(displ, cty)) +
  geom_point()

p +
  theme(
    axis.ticks = element_blank(),
    axis.ticks.length = unit(2, "cm") # exaggerated for clarity
  )

There are other ways to arrive at the same plot without the involvement of axis tick length, so it doesn't seem like the axis tick lengths are a necessary part for this purpose.

p +
  theme(
    axis.ticks = element_blank(),
    axis.text.x.bottom = element_text(margin = margin(t = 2, unit = "cm")),
    axis.text.y.left   = element_text(margin = margin(r = 2, unit = "cm"))
  )

^{Created on 2022-02-01 by the reprex package (v2.0.1)}

If the ggplot2 maintainers agree with me, I could draft a PR to remove the empty space when the axis ticks are blank.

[smouksassi]

setting length to negative value is a workaround but agree that this is a weird unexpected behavior and not consistent with other places where we use element blank to suppress the reserved space

library(ggplot2)
library(gridExtra)
p <- ggplot(mpg, aes(displ, cty)) +
  geom_point()

grid.arrange(p,
             p +theme(axis.text = element_blank()),
             p +theme(axis.text = element_blank(),axis.title = element_blank()) ,
             p +theme(axis.text = element_blank(),axis.title = element_blank(),axis.ticks = element_blank() ),
             p +theme(axis.text = element_blank(),axis.title = element_blank(),axis.ticks = element_blank(),
                               axis.ticks.length = unit(0.1, "npc")),
             p +theme(axis.text = element_blank(),axis.title = element_blank(),axis.ticks = element_blank(),
                      axis.ticks.length = - unit(0.1, "npc"))
                      
                      
                  ,ncol =1)  

^{Created on 2022-02-01 by the reprex package (v2.0.1)}

[hadley]

Axes are parameterised differently to other geoms since their length is not supplied by the element, but instead but a separate theme option. So I think the current behaviour, while a little surprising, is consistent and not worth changing.