在 ggplot2 中将 geom_text() 或 annotate() 添加到 coord_polar plot 时的奇怪行为

Question

I'm trying to replicate a Rose/Coxcomb/Circular Bar chart: example plot . I've managed to get the following to replicate the geom and the panel, but when I try to move the axis label from the left hand side of the plot margin and into the middle axis, it seems to send the aesthetic into chaos - it adds a "column" (ie pie-slice) and each variable straddles two other columns.

Here's a replica of code that works:

df <- tibble(name = "Sam",
             business = 2,
             product = 1,
             collaboration = 2,
             leadership = 2,
             strategy = 4,
             tactics = 1,
             users = 2,
             industry = 3)

df <- df %>% 
  pivot_longer(cols = business:industry, 
               names_to = "dimension", 
               values_to = "score")

df %>% 
  mutate(dimension = factor(dimension,
                            levels = unique(dimension),
                            labels = str_to_title(unique(dimension)))) %>%
  ggplot(aes(x = dimension,
           y = score)) +
  geom_col(fill = "red",
           alpha = 1,
           width = 1) +
  geom_hline(yintercept = seq(0, 5, by = 1),
             color = "grey", size = 1) +
  geom_vline(xintercept = seq(.5, 16.5, by = 1),
             color = "grey", size = 1) +
  coord_polar() +
  theme(panel.grid = element_blank(),
        panel.background = element_blank(),
        axis.text.y = element_blank(),
        axis.ticks.y = element_blank()) +
  expand_limits(y = c(-1,5))

which produces this output: code that works!

but when I add this line to the end of the ggplot call:

df %>% 
  mutate(dimension = factor(dimension,
                            levels = unique(dimension),
                            labels = str_to_title(unique(dimension)))) %>%
  ggplot(aes(x = dimension,
           y = score)) +
  geom_col(fill = "red",
           alpha = 1,
           width = 1) +
  geom_hline(yintercept = seq(0, 5, by = 1),
             color = "grey", size = 1) +
  geom_vline(xintercept = seq(.5, 16.5, by = 1),
             color = "grey", size = 1) +
  coord_polar() +
  theme(panel.grid = element_blank(),
        panel.background = element_blank(),
        axis.text.y = element_blank(),
        axis.ticks.y = element_blank()) +
  expand_limits(y = c(-1,5)) +
  annotate("text", 
           x = 0,
           y = 1:5,
           label = c(1, 2, 3, 4, 5))

It produces this plot: code that fails!

What's weird is if I add just a single label (ie - x = 1) then it works perfectly, but I don't fancy having to manually add 10 new geom_text lines to individually label each axis tick.

I'd love to be able to have one vertical set of axis labels running from the centre up the x = 0 point and one horizontal set of labels along the y = 0 line.

Any help greatly appreciated!

Apologies for the links instead of images, this is my first post to StackOverflow and I don't have enough reputation points to embed images!

Answer 1

Your categories are placed on 1, 2, .. in numerical terms. Hence, to place you annotations on the grid line between two categories you have to use.5 for the "x=0" line and 2.5 for the "y=0" line:

library(dplyr, warn = FALSE)
library(tidyr)
library(ggplot2)
library(stringr)

df %>% 
  mutate(dimension = factor(dimension,
                            levels = unique(dimension),
                            labels = str_to_title(unique(dimension)))) %>%
  ggplot(aes(x = dimension,
             y = score)) +
  geom_col(fill = "red",
           alpha = 1,
           width = 1) +
  geom_hline(yintercept = seq(0, 5, by = 1),
             color = "grey", size = 1) +
  geom_vline(xintercept = seq(.5, 16.5, by = 1),
             color = "grey", size = 1) +
  coord_polar() +
  theme(panel.grid = element_blank(),
        panel.background = element_blank(),
        axis.text.y = element_blank(),
        axis.ticks.y = element_blank()) +
  expand_limits(y = c(-1,5)) +
  annotate("text", 
           x = .5,
           y = 1:5,
           label = c(1, 2, 3, 4, 5)) +
  annotate("text", 
           x = 2.5,
           y = 1:5,
           label = c(1, 2, 3, 4, 5))