Test transparency geom_point()

geom_point_transparency.R

library(tidyverse)
library(patchwork)

df <- tibble(x = 1, y = 1)

g <- ggplot(df, aes(x, y)) +
  scale_x_continuous(expand = c(0, 0)) +
  scale_y_continuous(expand = c(0, 0)) +
  coord_cartesian(clip = "off") +
  theme_void() +
  theme(plot.title = element_text(hjust = .5))

p1 <- g +
  geom_point(size = 100) +
  ggtitle("geom_point(alpha = 1, shape = 19)\n(DEFAULT)")

p2 <- g +
  geom_point(size = 100, alpha = .2, stroke = 5) +
  ggtitle("geom_point(alpha = .2, shape = 19)\n")

p3 <- g +
  geom_point(size = 100, alpha = .2, stroke = 5, shape = 16) +
  ggtitle("geom_point(alpha = .2, shape = 16)\n")

p4 <- g +
  geom_point(size = 100, alpha = .2, stroke = 5, shape = 21, fill = "black") +
  ggtitle("geom_point(alpha = .2, shape = 21, fill = 'black')\n")

p5 <- g +
  geom_point(size = 100, stroke = 5, color = "#00000033") +
  ggtitle("geom_point(color = '#00000033')\n")

p6 <- g +
  geom_point(size = 100, stroke = 5, shape = 21, color = "#000000", fill = "#00000033") +
  ggtitle("geom_point(shape = 21, color = '#000000', fill = '#00000033')\n")
 
p1 + p2 + p3 + p4 + p5 + p6

ggsave("points.pdf", width = 16, height = 8, device = cairo_pdf)