different size facets proportional of x axis on ggplot 2 r

Question

The following is a situation:

group1 <- seq(1, 10, 2)
group2 <-  seq(1, 20, 3)
x = c(group1, group2)
mydf <- data.frame (X =x , Y = rnorm (length (x),5,1), 
 groups = c(rep(1, length (group1)), rep(2, length(group2))))

ggplot(mydf, aes(X, Y, group= groups)) + geom_point()+ facet_grid (.~ group)

Different facets are scaled by x limits in the following plot:

 ggplot(mydf, aes(X, Y, group= groups)) + geom_point()+ 
   facet_grid (.~ group, scales = "free_x")

As total width of x has meaning, I want to produce facets of different width not only different scale. Thus the expected facet 1's wideth should be half the size of 2.

Answer 1

If I understand you correctly, space = "free_x" does what you want.

library(ggplot2)

ggplot(mydf, aes(X, Y)) + geom_point()+ 
facet_grid (.~ groups, scales = "free_x", space = "free_x")

And if you want the same style of labelling on the x axes:

ggplot(mydf, aes(X, Y)) + geom_point()+ 
 scale_x_continuous(breaks = seq(0,20,2)) +
 facet_grid (.~ groups, scales = "free_x", space = "free_x")