更改堆叠条形图中段的顺序

Question

How can I change the order of the segments in the following stacked barplot from -- (left) to ++ (right) and NA on the right?

library(dplyr)
library(ggplot2)
library(tidyr)

size <- 100

df <- data.frame(item1 = sample(c(1:5, 1:5, 99), size = size, replace = TRUE),
                 item2 = sample(c(1:5, 1:4, 99), size = size, replace = TRUE),
                 item3 = sample(c(1:5, 1:3, 99), size = size, replace = TRUE),
                 item4 = sample(c(1:5, 1:5, 99), size = size, replace = TRUE),
                 item5 = sample(c(1:5, 1:4, 99), size = size, replace = TRUE)) 


# Stacked barplot

df %>% pivot_longer(cols = starts_with("item")) %>%
  group_by(name) %>%
  count(value) %>%
  mutate(perc = 100 / sum(n) * n) %>%
  ungroup() %>%
  mutate(value = factor(value, levels = c(1:5, 99), labels = c("--", "-", "0", "+", "++", "NA"))) %>%
  
  ggplot(aes(x = name, y = perc, fill = value)) + geom_col() +
  coord_flip()

^{Created on 2022-12-12 with reprex v2.0.2}

Answer 1

You can reverse the order of the stack by using position_stack(reverse = TRUE) :

set.seed(123)

library(tidyr)
library(ggplot2)
library(dplyr)

df %>% pivot_longer(cols = starts_with("item")) %>%
  group_by(name) %>%
  count(value) %>%
  mutate(perc = 100 / sum(n) * n) %>%
  ungroup() %>%
  mutate(value = factor(value, levels = c(1:5, 99), labels = c("--", "-", "0", "+", "++", "NA"))) %>%
  ggplot(aes(x = name, y = perc, fill = value)) + 
  geom_col(position = position_stack(reverse = TRUE)) +
  coord_flip()