Remove geom(s) from an existing ggplot chart?

Question

I am trying to understand how I can make changes to the internals of a ggplot2 chart. I started reading the few ressources I could find about ggplot_built and <

Answer 1

You can try to include some alpha. Instead of removing the layer, it will not show up.

count(mpg, class) %>%
  mutate(pct=n/sum(n)) %>%
  ggplot(aes(class, pct)) +
  geom_col(fill="blue", alpha=0) +
  geom_line(group=1) +
  geom_point(size=4)

You can of course add the alpha afterwards like

p <- ggplot_build(p)
p$data[[1]]$alpha <- 0
plot(ggplot_gtable(p))