基于轴颜色的ggplot图例

Posted 2023-02-16

【中文标题】基于轴颜色的ggplot图例

【英文标题】：ggplot legend based on axis colors

【发布时间】：2021-08-31 14:39:27

【问题描述】：

我正在尝试根据我设置的 y 轴的颜色在 ggplot 中创建一个图例。

有谁知道是否有一种方法可以根据图中本身不存在的数据手动创建图例？

下面是情节和代码的玩具示例。在这个图中，我绘制了 3 个不同日期的学生成绩图。学生的姓名根据他们所在的班级进行着色。我想知道我是否可以添加一个额外的图例，以绿色显示“A 班”，以紫色显示“B 班”。

作为补充说明，我意识到日子并不好过。目前我并不担心这一点。

谢谢！

library(tidyverse)

name <- c("Mike", "Mike","Mike",
          "Sam","Sam","Sam", 
          "Max","Max","Max", 
          "Sarah","Sarah","Sarah") 
date <- c("Monday", "Wednesday", "Friday",
          "Monday", "Wednesday", "Friday",
          "Monday", "Wednesday", "Friday",
          "Monday", "Wednesday", "Friday")
grade <- c(100, 98, 93, 
           92, 64, 90, 
           80, 88,70,
           90,94,100)
clas-s-room <- c("Class A", "Class A","Class A", 
               "Class A", "Class A","Class A", 
               "Class B", "Class B","Class B", 
               "Class B", "Class B","Class B")

df <- data.frame(cbind(name, date, grade, clas-s-room)) %>%
  mutate(grade = as.integer(grade),
         clas-s-room = as.factor(clas-s-room))


plot <- ggplot(df, aes(y=name, x=date, fill= grade < 90)) + 
  geom_tile() +
  scale_fill_manual(name = " ", values = c( "turquoise3","lightgrey"), labels = c("Above 90","At or below 90" )) +
  theme(axis.text.y = element_text(color = ifelse(levels(df$clas-s-room) %in% "Class A", "Green", "Purple"))) +
  guides(size = "none", color = "none", alpha = "none") 

【问题讨论】：

你也许可以使用ggtext

【参考方案1】：

你可以facet_wrap

plot <- ggplot(df, aes(y=name, x=date, fill= grade < 90)) + 
  geom_tile() +
  scale_fill_manual(name = " ", values = c( "turquoise3","lightgrey"), labels = c("Above 90","At or below 90" )) +
  theme(axis.text.y = element_text(color = ifelse(levels(df$clas-s-room) %in% "Class A", "Green", "Purple"))) +
  guides(size = "none", color = "none", alpha = "none") 

plot +  facet_wrap(~clas-s-room)

或facet_grid

plot + facet_grid(rows = vars(clas-s-room))