r - 堆叠条形图的颜色取决于向量的数量和长度

Question

我有一个看起来像这样的数据框

df <- data.frame("V1" = c(0,0,0,0,0,2,2,2,2,2),
                 "V2" = c(9,9,9,0,0,2,2,2,0,0))

我想以这种方式创建一个堆叠条形图:

所以基本上我将某个值映射到相应的颜色(9 -> 白色(不可见)、0 -> 绿色 2 -> 红色)，然后创建一个长度为等于数据框列中值的出现次数。有没有办法做这样的事情，即使用 ggplot2？

Answer 1

您可以使用pivot_longer将数据帧更改为长格式。例如，使用 case_when 添加一列，其中包含要显示条形的颜色。您可以使用 scale_fill_identity 将条形填充为相应的颜色。要在堆叠条中获得与数据框相同的填充顺序，您可以使用 ggplot_build 来修改绘图的数据，方法是将“填充”列替换为与数据框顺序相同的向量。您可以使用以下代码:

library(ggplot2)
library(tidyr)
library(dplyr)
library(scales)
# Create plot
p <- df %>%
  mutate(index = 1) %>%
  pivot_longer(cols = -index) %>%
  mutate(color = case_when(value == 9 ~ 'white',
                           value == 0 ~ 'darkgreen',
                           TRUE ~ 'red')) %>%
  ggplot(aes(x = index, y = name, fill = color)) +
  geom_col(width = 0.3) +
  scale_fill_identity() +
  theme_classic() +
  scale_x_continuous(expand = c(0,0), breaks = pretty_breaks(2)) +
  labs(x = '', y = '')

# Extract vector of colors in right order
vec_colors <- df %>%
  mutate(index = 1) %>%
  pivot_longer(cols = -index) %>%
  mutate(color = case_when(value == 9 ~ 'white',
                           value == 0 ~ 'darkgreen',
                           TRUE ~ 'red')) %>%
  arrange(name) %>%
  pull(color)

# right order colors
vec_colors
#>  [1] "darkgreen" "darkgreen" "darkgreen" "darkgreen" "darkgreen" "red"      
#>  [7] "red"       "red"       "red"       "red"       "white"     "white"    
#> [13] "white"     "darkgreen" "darkgreen" "red"       "red"       "red"      
#> [19] "darkgreen" "darkgreen"

# use ggplot_build to modify data and replace fill column with vector
q <- ggplot_build(p)
q$data[[1]] <- q$data[[1]] %>%
  group_by(y) %>%
  arrange(x, .by_group = TRUE) 

q$data[[1]]$fill <- vec_colors

q <- ggplot_gtable(q)

# plot 
plot(q)

^{创建于 2022 年 9 月 17 日 reprex v2.0.2}

---

要添加图例，您应在 scale_fill_identity 中指定 guide = 'legend'。要确定要在图例中显示哪些元素，您应该指定 labels 和 breaks，如下所示:

library(ggplot2)
library(tidyr)
library(dplyr)
library(scales)
# Create plot
p <- df %>%
  mutate(index = 1) %>%
  pivot_longer(cols = -index) %>%
  mutate(color = case_when(value == 9 ~ 'white',
                           value == 0 ~ 'darkgreen',
                           TRUE ~ 'red')) %>%
  ggplot(aes(x = index, y = name, fill = color)) +
  geom_col(width = 0.3) +
  scale_fill_identity(guide = 'legend',
                      labels = c('darkgreen', 'red'),
                      breaks = c('darkgreen', 'red')) +
  theme_classic() +
  scale_x_continuous(expand = c(0,0), breaks = pretty_breaks(2)) +
  labs(x = '', y = '')

# Extract vector of colors in right order
vec_colors <- df %>%
  mutate(index = 1) %>%
  pivot_longer(cols = -index) %>%
  mutate(color = case_when(value == 9 ~ 'white',
                           value == 0 ~ 'darkgreen',
                           TRUE ~ 'red')) %>%
  arrange(name) %>%
  pull(color)

# use ggplot_build to modify data and replace fill column with vector
q <- ggplot_build(p)
q$data[[1]] <- q$data[[1]] %>%
  group_by(y) %>%
  arrange(x, .by_group = TRUE) 

q$data[[1]]$fill <- vec_colors

q <- ggplot_gtable(q)

# plot 
plot(q)

^{创建于 2022-09-24 reprex v2.0.2}