Set breaks between values in continuous axis of ggplot

How can we set the breaks of continous axis every 2 numbers if we have a very big range of values in an axis and cannot set it manually?

p1 <- ggplot(mpg, aes(displ, hwy)) +
  geom_point()
p1 + scale_x_continuous(breaks = c(2, 4, 6))

>Solution :

From the ?scale_x_continuous help page, breaks can be (among other options)

A function that takes the limits as input and returns breaks as output

Here’s an anonymous function going from the (floored) min to the (ceilinged) max by 2:

ggplot(mpg, aes(displ, hwy)) +
  geom_point() + 
  scale_x_continuous(breaks = \(x) seq(floor(x[1]), ceiling(x[2]), by = 2))

Alternately you could still use seq for finer control, more customizable, less generalizable:

ggplot(mpg, aes(displ, hwy)) +
  geom_point() + 
  scale_x_continuous(breaks = seq(2, 6, by = 2))