How to remove the margin between plot region and panel in ggplot2?

Question

I am creating some maps and want to remove all margins between the plot region and panel border.

This is the minimal example to reproduce my question

Answer 1

(Alright, here's my comment as an answer..)

Just add the following to the plot:

+ scale_y_continuous(expand = c(0,0)) + scale_x_continuous(expand = c(0,0))