ggplot2 - The unit of size

Question

A quick question that I can\'t find answer on the web (or Wickham\'s book):

What is the unit of the size argument in ggplot2? For example, geom_tex

Answer 1

From ?aes_linetype_size_shape

# Size examples
# Should be specified with a numerical value (in millimetres),
# or from a variable source

height and width in ggsave relate to par("din") from ?par

din

  R.O.; the device dimensions, (width, height), in inches. See also dev.size,
  which is updated immediately when an on-screen device windows is re-sized.

So I guess size in aes is in millimetres and ggsave height and width are in inches.