Custom y axis breaks of facet_wrap

Question

I have created a faceted plot with facet_wrap, and I would like to change the breaks of y axis of all facets.

This is my current plot:

ggplot( mtcars , aes(x=mpg, y=wt, color=as.factor(cyl) )) +
  geom_point(size=3) +
  facet_wrap(~cyl,scales = "free_y") +
  theme(legend.position="none")

This is my desired y axis breaks:

p = ggplot(data=mtcars, aes(x=mpg, y=wt)) +
  geom_point(size=3) +
  theme_classic()
ymax <- ceiling(max(mtcars$wt))
p + scale_y_continuous(breaks = c(0, ymax), expand = c(0, 0)) + expand_limits(y = ymax)

Bismuthic

The desired example doesn't seem to be related to mtcars. What is df$len? – Narghile

Sorry, I have corrected this. – Bismuthic

What is then wrong? p + scale_y_continuous(breaks = c(0, ymax), expand = c(0, 0)) + expand_limits(y = ymax) produces a 0-6 y-scale. – Narghile

I want to create different y axis breaks to different facet, eg: 0-4 in facet 4, 0-4 in facet 6 and 0-6 in facet 8. – Bismuthic

perhaps have a look at https://mcmap.net/q/495836/-ggplot2-change-axis-limits-for-each-individual-facet-panel – Narghile

Nice, I will hava a try! – Bismuthic

Answer 1

If you have a 'rule' for the y-axis breaks/limits you can provide a function to these arguments of the scale, which will evaluate that function for every facet. Note that the limits function gets the 'natural' data limits as argument, whereas the breaks function gets the expanded limits as argument.

library(ggplot2)

p <- ggplot( mtcars , aes(x=mpg, y=wt, color=as.factor(cyl) )) +
  geom_point(size=3) +
  facet_wrap(~cyl,scales = "free_y") +
  theme(legend.position="none")

p + scale_y_continuous(
  limits = ~ c(min(.x), ceiling(max(.x))),
  breaks = ~ .x[2],
  expand = c(0, 0)
)

Alternatively, if you need to tweak the y-axis of every panel, you might find ggh4x::facetted_pos_scales() useful. Disclaimer: I'm the author of ggh4x.

p + ggh4x::facetted_pos_scales(y = list(
  cyl == 4 ~ scale_y_continuous(limits = c(0, NA)),
  cyl == 6 ~ scale_y_continuous(breaks = c(2.9, 3, 3.1)),
  cyl == 8 ~ scale_y_continuous(trans = "reverse")
))

^{Created on 2022-07-16 by the reprex package (v2.0.1)}

Vladi

Answer 2

Sorry, you haven't give any information about 'df'. so I can't run the code in the 2rd section.(ymax <- ceiling(max(df$len)))

In general, to change the breaks of y axis, you could use scale_y_continuous(breaks = c(), labels = c(), limits = (), ...). And use facet_wrap(~var) to plot facet.

Please supply more information about 'df'.

Oler

Yes, the question is how to apply different y axis breaks to different facet? – Bismuthic