Add guide lines for y-axis when using coord_polar() for polar histogram

Question

I want to create a polar histogram like this

with dashed lines going from the y-axis ticks to the 0/360 line to help the reader to map the count to the histogram's bar length. I have added the dashed lines with power point but I am wondering whether it is possible to add this with ggplot.

I used this code

library(ggplot2)
# Seed
set.seed(20220315)

# Create random data from 0 to 360
example_dat <- data.frame(rot_y = runif(1000, min = 0, max = 360))


# Create polar plot
ggplot(example_dat, aes(x = rot_y )) +
  geom_histogram(binwidth = 15, boundary = -7.5, colour = "black", size = .25) +
  scale_x_continuous(limits = c(0,360),
                     breaks = seq(0, 360, by = 60),
                     minor_breaks = seq(0, 360, by = 15))  +
  coord_polar() +
  labs(title = 'Polar histogram of y rotation',
       y = 'Count',
       x = '')

to generate this plot

I am aware of the work around for drawing a line segment like in this solution: draw straight line between any two point when using coord_polar() in ggplot2 (R)

However, when drawing a straight line with function given in that solution using aes(x = 270, y = 0, xend = 720, yend = 60), the line just disappears, while a line can be seen for something like aes(x = 270, y = 0, xend = 720, yend = 10) but the problem is then it does not extent to the label ticks, which make sense as I told the line to end at 10.

Answer 1

Here's a slightly manual approach using patchwork, assuming the original plot is saved to p. The alignment of the plots uses magic numbers determined by trial and error.

library(patchwork)
l <- ggplot() +
  annotate("segment", x = 0, xend = -60, 
           y = 10*c(0:5), yend = 10*c(0:5),
           linetype = "dashed") +
  theme_void()
p + inset_element(l, left = 0, top = 0.91, bottom = 0.48, right = 0.52)