R：将自定义图例添加到ggplot

问题描述

我有以下情节：

并要添加如下图例：

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,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,size = 4) +
  scale_y_continuous(breaks = 0:20,limits = c(0,20)) +
  coord_fixed(.15) +
  theme_classic()

plot(gg)

解决方法

是的（可能）：

gg <- 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(aes(alpha = "Grade",yintercept = 13),linetype = 2,color = green,size = 1,key_glyph = "pointrange") +
  geom_point(aes(student,grade,shape = "Grade"),color = blue,size = 4) +
  geom_point(aes(student,gradeHat),size = 4)  +
  scale_y_continuous(breaks = 0:20,limits = c(0,20)) +
  scale_shape_manual(values = 19,name = NULL,guide = guide_legend(order = 1)) +
  scale_color_manual(values = redblood,guide = guide_legend(order = 3)) +
  scale_alpha_manual(breaks = "Grade",values = 1,guide = guide_legend(order = 2,override.aes = list(color = green)),name = "") +
  scale_fill_manual(values = redblood,name = NULL) +
  coord_fixed(.15) +
  theme_classic() +
  theme(legend.position = "bottom",legend.key.width = unit(20,"points")) 

plot(gg)

不是您问题的完整解决方案...但是我目前能提供的最好的解决方案：

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，而必须映射到color内的fill或aes()上。为此，您可以使用占位符或标签，例如fill="SS"中的geom_rect。
要获得正确的颜色，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，但是可以通过theme()和legend.spacing在legend.margin中删除它们
最后一部分是为图例标签着色。这可以通过ggtext包来实现，该包通过主题选项legend.text = element_markdown()允许使用HTML和CSS设置图例条目的样式。

不幸的是，我无法弄清楚如何在您的gradeHat上戴上宽阔的帽子。

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,id]
DT[,ymax := max(grade,student := factor(student,levels = student)]

ggplot(DT) +
  geom_segment(aes(x = student,color = "error"),alpha = .4) +
  geom_hline(yintercept = b0,alpha = .7,linetype = "dashed") +
  geom_point(aes(student,color = "grade"),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 = 0:20,20)) +
  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)

ggplot2 ggtext legend r r