geom_rect() ignores the alpha argument?

[Leon]

Hi all,

It seems that the geom_rect() function ignores the alpha argument?

Example:

library('tidyverse')
tibble(x = rnorm(100), y = rnorm(100)) %>% 
  ggplot(aes(x = x, y = y)) +
  geom_vline(xintercept = 0) +
  geom_hline(yintercept = 0) +
  geom_rect(aes(xmin = -2, xmax = 2, ymin = -2, ymax = 2),
            fill = "palegreen", colour = "black", alpha = 0.5) +
  geom_point(size = 3, alpha = 0.5) +
  theme_bw() +
  coord_fixed(xlim = c(-4, 4), ylim = c(-4, 4))

Yielding:

[pieterjanvc]

Hi,

If I set alpha to a really low value, like 0.01, it is working, but for some reason the scale of the value does not match the transparency you'd expect...

Grtz
PJ

[hadley]

You are drawing 100 rectangles

[Leon]

@hadley

You are drawing 100 rectangles

I.e. one rectangle per nrow(.)? Wow... How do I avoid this then?

Edit: Tried with inherit.aes = FALSE, but no cigar...

[pieterjanvc]

Hi,

Found something that works, but probably not the most elegant solution

library('tidyverse')
tibble(x = rnorm(100), y = rnorm(100)) %>% 
  ggplot(aes(x = x, y = y)) +
  geom_vline(xintercept = 0) +
  geom_hline(yintercept = 0) +
  geom_rect(data = data.frame(x = 0, y = 0), aes(xmin = -2, xmax = 2, ymin = -2, ymax = 2),
            fill = "palegreen", colour = "black", alpha = 0.5) +
  geom_point(size = 3, alpha = 0.5) +
  theme_bw() +
  coord_fixed(xlim = c(-4, 4), ylim = c(-4, 4))

PJ

[nwerth]

You can use the annotate function from ggplot2:

tibble(x = rnorm(100), y = rnorm(100)) %>% 
  ggplot(aes(x = x, y = y)) +
  geom_vline(xintercept = 0) +
  geom_hline(yintercept = 0) +
  annotate(geom = "rect", xmin = -2, xmax = 2, ymin = -2, ymax = 2,
           fill = "palegreen", colour = "black", alpha = 0.5) +
  geom_point(size = 3, alpha = 0.5) +
  theme_bw() +
  coord_fixed(xlim = c(-4, 4), ylim = c(-4, 4))

[Leon]

@nwerth

You can use the annotate function from ggplot2

Yup, that does the trick - Excellent!

[Leon]

Ps. for future reference: The issue was basically, that I was swapping the intention of the functions, as per @hadley's hint. geom_rect() is for drawing rectangles and annotate() is for annotating and I wanted to do the latter (The hint is in the title).

Thanks for input

geom_rect() example:

library('ggplot2')
set.seed(75322)
n = 100
tibble(x1 = rnorm(n = n), x2 = rnorm(n = n),
       y1 = rnorm(n = n), y2 = rnorm(n = n)) %>% 
  ggplot(aes(xmin = x1, xmax = x2, ymin = y1, ymax = y2)) +
  geom_rect(alpha = 0.25, colour = "black",
            fill = sample(x = 2:7, size = 100, replace = TRUE)) +
  theme_void() +
  coord_fixed()
ggsave(filename = 'my_rectangles.png', width = 3, height = 3)

Yielding:

[martin.R]

Now that's proper aRt.