How to start with the first axis tick at the origin in ggplot

Question

I would like to always start with the first axis tick at the origin, such as in this image:

Playing around with xlim, expand_limits or scale_x_continuous doesn't really work - there's always a little spacing between first axis tick and origin. There should be an easy way to do this. Many thanks in advance.

Answer 1

The solution that worked for me is to set the option expand=c(0,0) together with the limits option, e.g.:

  scale_y_continuous(expand = c(0, 0), limits = c(10,NA))

Y axis then starts at the origin with the first tick with label 10.

Answer 2

Unfortunately, ggplot2 is set up expand the axes and thus pad the axis ticks, and there's not a simple function to force them to be flush at the origin. I find the best way to get axis ticks at the origin is to use coord_cartesian() to turn off axis expansion and manually specify limits

require(ggplot2)

ggplot(mtcars, aes(wt, mpg)) +
  geom_point() +
  theme_classic() +
  coord_cartesian(expand = FALSE, #turn off axis expansion (padding)
                  xlim = c(1, 6), ylim = c(10, 35)) #manually set limits

I prefer to define limits in coord_cartesian() rather than in scale_y_...() and scale_x_...() because coord_cartesian() crops the view but does not alter the underlying data. scale...() functions remove data outside the limits, which could mess up fitted lines (stat_smooth()) or summary stats if you crop out an outlier.