R：将自定义图例添加到ggplot

debugcn 发表于 Dev

垫

我有以下情节：

并想添加一个图例如下：

这是我用来生成绘图的代码：

library(data.table)
library(ggplot2)

blue <- "#4472C4"
green <- "#548235"
red <- "#C55A11"
redblood <- "#C00000"

DT <- data.table(student = c("Jane", "Sam", "Tim", "Kate", "Claire"),
                 grade = c(10, 14, 8, 9, 19))

b0 <- 13

DT[, gradeHat := b0]
DT[, e := grade - gradeHat]
DT[, SS := sum(e**2)]

DT[, id := 1:nrow(DT)]
DT[, xmin := id]
DT[, xmax := id + abs(e)/20*3]
DT[, ymin := min(grade, gradeHat), id]
DT[, ymax := max(grade, gradeHat), id]
DT[, student := factor(student, levels = student)]

gg <- ggplot(DT) +
  geom_segment(aes(x = student, xend = student, y = grade, yend = gradeHat),
               color = redblood, size = 1.3) +
  geom_rect(aes(xmin = xmin, xmax = xmax, ymin = ymin, ymax = ymax),
            fill = redblood, alpha = .4) +
  geom_hline(yintercept = b0, color = green, alpha = .7, size = 1, linetype = "dashed") +
  geom_point(aes(student, grade), color = blue, size = 4) +
  geom_point(aes(student, gradeHat), color = green, size = 4) +
  scale_y_continuous(breaks = 0:20, limits = c(0, 20)) +
  coord_fixed(.15) +
  theme_classic()

plot(gg)

斯蒂芬

并非您问题的完整解决方案...但目前我能提出的最好方案是：

要在ggplot中获得图例，您必须映射美学，即，不必将颜色设置为参数，而必须在上color或fill内部映射aes()。为此，您可以使用占位符或标签，例如fill="SS"在中geom_rect。
要获得正确的颜色，您可以使用scale_color/fill_manual。使用标签可以轻松分配正确的颜色。
接下来，要正确设置图例的样式，可以使用guide_legend及其参数override.aes来设置颜色图例的形状和线型。
默认情况下，color和fill图例之间有一些间距，但是可以theme()通过legend.spacing和删除legend.margin。
最后一部分是为图例标签着色。这可以通过ggtext通过主题选项legend.text = element_markdown()允许使用HTML和CSS设置图例条目样式的包来实现。

不幸的是我无法弄清楚如何在你的帽子上戴宽阔的帽子gradeHat。

library(data.table)
library(ggplot2)

blue <- "#4472C4"
green <- "#548235"
red <- "#C55A11"
redblood <- "#C00000"

DT <- data.table(student = c("Jane", "Sam", "Tim", "Kate", "Claire"),
                 grade = c(10, 14, 8, 9, 19))

b0 <- 13

DT[, gradeHat := b0]
DT[, e := grade - gradeHat]
DT[, SS := sum(e**2)]

DT[, id := 1:nrow(DT)]
DT[, xmin := id]
DT[, xmax := id + abs(e)/20*3]
DT[, ymin := min(grade, gradeHat), id]
DT[, ymax := max(grade, gradeHat), id]
DT[, student := factor(student, levels = student)]

ggplot(DT) +
  geom_segment(aes(x = student, xend = student, y = grade, yend = gradeHat, color = "error"),
               , size = 1.3) +
  geom_rect(aes(xmin = xmin, xmax = xmax, ymin = ymin, ymax = ymax, fill = "SS"), alpha = .4) +
  geom_hline(yintercept = b0, color = green, alpha = .7, size = 1, linetype = "dashed") +
  geom_point(aes(student, grade, color = "grade"), size = 4) +
  geom_point(aes(student, gradeHat, color = "gradeHat"), size = 4) +
  scale_color_manual(breaks = c("grade", "gradeHat", "error"), 
                     values = c(grade = blue, gradeHat = green, error = red),
                     labels = c(grade = glue::glue("<span style = 'color: {blue};'>grade</span>"),
                                gradeHat = glue::glue("<span style = 'color: {green};'>gradeHat</span>"), 
                                error = glue::glue("<span style = 'color: {red};'>error</span>"))) +
  scale_fill_manual(values = c(SS = redblood), labels = c(SS = glue::glue("<span style = 'color: #C0000066; '>SS</span>"))) +
  guides(color = guide_legend(order = 1, override.aes = list(shape = c(16, 16, NA), linetype = c("blank", "dashed", "solid")))) +
  scale_y_continuous(breaks = 0:20, limits = c(0, 20)) +
  coord_fixed(.15) +
  theme_classic() +
  theme(legend.position = "bottom", 
        legend.spacing = unit(0, "pt"), 
        legend.margin = margin(r = 0, l = 0),
        legend.text = ggtext::element_markdown()) +
  labs(color = NULL, fill = NULL)