I can force ggplot2 scatter plot to be square shaped with the same x and y scaling using
If you want to make the distance scale points the same, then use coord_fixed():
p <- ggplot(...) p <- p + coord_fixed() # ratio parameter defaults to 1 i.e. y / x = 1
If you want to ensure that the resulting plot is square then you would also need to specify the x and y limits to be the same (or at least have the same range).
ylim are both arguments to
coord_fixed. So you could do this manually using those arguments. Or you could use a function to extract out limits from the data.