ggplot2: Circular barplot manipulation for scalability

Preamble: I recently having this thread

Goal

Replicating this plot

Current code

library(tidyverse)

data <- data.frame(
  labels = c("A","B","C","D","E","F","G","H"),
  values = c(88, 61, 56, 77, 83, 63, 42, 60)
) %>%
  mutate(
    bar_color = case_when(
      values < 62 ~ "#f2452e",
      values < 85 ~ "#76c5d0",
      values >= 85 ~ "#4b7d84",
    )
  )

ggplot(data, aes(x = labels, y = values)) +
  geom_bar(aes(fill = bar_color),
           stat = "identity", size = 1,
           color = "gray20", width = 1,
           alpha = 0.8) +
  coord_polar(start = -(pi / 8)) +
  scale_fill_identity() +
  theme(
    panel.grid.major.y = element_line(
      linewidth = .8,
      color = c("transparent", alpha("grey80", 0.5))
    ),
    axis.title = element_blank(),
    panel.background = element_blank(),
    axis.ticks.y = element_blank(),
    axis.text = element_blank(),
  ) +
  geom_hline(yintercept = 96.5,
             color = "grey90", size = 3) +
  scale_y_continuous(breaks = seq(0, 95, 5)) +
  geom_segment(aes(x = 1.5:8.5, y = 0, yend = 95),
               inherit.aes = FALSE, color = alpha("grey20", 0.5)) +
  geom_hline(yintercept = 94,
             color = "grey20", size = 1) +
  geom_label(aes(label = labels, y = 96), fill = "white", size = 6)

Current plot:

Problem

The value of:

1. breaks in scale_y_continuous()
2. yintercept in geom_hline()
3. yend in geom_segment(); and
4. y in geom_label()

Is all hardcoded. It become challenge when data$values changing, especially above 95 (max is 100). I need help on making sure that the values of problem #1 to #4 stays at around 100 to cover all possible values of data$values

Example of issue

I change the value of above's parameters to around 99-100 because i want to make the length of bar relative to 0 - 100.

1. breaks = seq(0, 100, 5)
2. yintercept = 101.5 in the first
3. yintercept = 99 in the second geom_hline()
4. yend = 100 in geom_segment(); and
5. y = 101 in geom_label()

so become this:

ggplot(data, aes(x = labels, y = values)) +
  geom_bar(aes(fill = bar_color),
           stat = "identity", size = 1,
           color = "gray20", width = 1,
           alpha = 0.8) +
  coord_polar(start = -(pi / 8)) +
  scale_fill_identity() +
  theme(
    panel.grid.major.y = element_line(
      linewidth = .8,
      color = c("transparent", alpha("grey80", 0.5))
    ),
    axis.title = element_blank(),
    panel.background = element_blank(),
    axis.ticks.y = element_blank(),
    axis.text = element_blank(),
  ) +
  geom_hline(yintercept = 101.5,
             color = "grey90", size = 3) +
  scale_y_continuous(breaks = seq(0, 100, 5)) +
  geom_segment(aes(x = 1.5:8.5, y = 0, yend = 100),
               inherit.aes = FALSE, color = alpha("grey20", 0.5)) +
  geom_hline(yintercept = 99,
             color = "grey20", size = 1) +
  geom_label(aes(label = labels, y = 101), fill = "white", size = 6)

New result is like this:

Notice that theres extra circle in the outer line and i kinda struggle with this

I would do away with a background grid altogether and draw the breaks yourself. It is not clear from your question whether you want to normalize the values so that the maximum value is always at 100. If so, you would do:

library(tidyverse)

data <- data.frame(labels = c("A","B","C","D","E","F","G","H"),
                   values = c(88, 61, 56, 77, 83, 63, 42, 60)) %>%
        mutate(bar_color = case_when(values < 62 ~ "#de583f",
                                     values < 85 ~ "#759d9f",
                                     values >= 85 ~ "#4b7d84",))

scaling_factor <- max(data$values)

ggplot(data %>% mutate(values = values / scaling_factor), 
       aes(labels, values, fill = bar_color)) +
  geom_col(width = 1, aes(color = after_scale(fill))) +
  annotate("linerange", ymin = 0, ymax = 1, x = seq(nrow(data)) - 0.5,
           color = "#494949") +
  geom_hline(yintercept = c(0, 2, 4, 6, 8) / 10, color = "#494949", alpha = 0.2) +
  geom_hline(yintercept = 1.02, color = "#d9d9d9", linewidth = 4) +
  geom_hline(yintercept = 1, color = "#494949") +
  geom_label(aes(y = 1, label = labels), fill = "#edecea", color = "#494949",
             size = 8, family = "Courier New") +
  scale_fill_identity() +
  coord_polar(start = -pi/8) +
  theme_void() +
  scale_y_continuous(limits = c(0, 1.1), expand = c(0, 0)) +
  theme(plot.background = element_rect(fill = "#edecea", color = NA))

If the numbers are absolute values and you want the range of your plot to be 100, just change the line scaling_factor <- max(data$values) to scaling_factor <- 100. Then the exact same plotting code will give you: