Question

I am trying to add a geom_tile layer to a plot without the filled color (just the outline). Is there a way to get a transparent tile where only the boundary is visible?

Thanks

Answer 1

I think you are after alpha parameter. Minimal example:

1. Create a plot with dummy data where you set color (for “boundary”) and no fill:

   p <- ggplot(pp(20)[sample(20*20, size=200), ], aes(x = x, y = y, color = z))
   

2. Add geom_tile() with alpha set to zero:

   p <- geom_tile(alpha=0)
   

3. Add theme_bw() as transparent tiles look lame with a dark gray background 🙂

   p + theme_bw()