ggplot将变量添加到图例而不包括在图中（使用alpha时）

Question

我想在图例中添加一个变量而不将其包括在图中。

我认为当我不使用alpha时也不会出现问题（请参阅：How do I add a variable to the legend without including it in the graph?）

library(tidyverse)

name_color <- c('black', "blue", "orange", "pink")
names(name_color) <- letters[1:4]

tibble(name = rep(letters[1:4], each = 2),
       respond = rep(c("yes", "no"), 4),
       n = rep(50, 8),
       me = "i") %>%
  filter(name != "c") %>% 
  ggplot(aes(me, n, fill = name, alpha = respond)) +
  facet_wrap(~name) +
  geom_bar(stat = "identity") +
  scale_fill_manual(values = name_color, drop = FALSE)

Answer 1

该问题与void switchArray(int array2D[][4], int numRow, int numCol){ for(int i=0; i < numRow; i++){ switchRow(array2D[i], COL); } } void switchRow(int arr[], int length){ if (length == 0) return; if (arr[0] == 1) arr[0] = 2; else arr[0] = 1; switchRow(++arr, length - 1); } 无关。问题在于您的数据类别。当您使用alpha创建数据时，tibble列属于name类。您需要一个character类来“记住”未使用的级别：

factor

在您链接的第一个问题中，您明确地进行了因子转换，这就是它起作用的原因。

name_color <- c('black', "blue", "orange", "pink")
names(name_color) <- letters[1:4]
d = tibble(name = rep(letters[1:4], each = 2),
       respond = rep(c("yes", "no"), 4),
       n = rep(50, 8),
       me = "i") %>%

class(d$name)
# [1] "character"

d %>% mutate(name = factor(name)) %>%  
  filter(name != "c") %>% 
  ggplot(aes(me, n, fill = name, alpha = respond)) +
  facet_wrap(~name) +
  geom_bar(stat = "identity") +
  scale_fill_manual(values = name_color, drop = FALSE)