将图例添加到基于图的误差条颜色

Question

我准备了示例数据。我想根据 error bar 颜色为此图添加图例。我尝试手动添加图例，但它不起作用。谢谢你的帮助。

data = data.frame(x = c(5,  10, 15, 20, 25, 30, 35, 40, 50),
                  Y1 = c(179,   212,    201,    204,    220,    181,    176,    219,    182),
                  SD1 = c(58,   93, 74, 55, 59  ,56,    53, 62, 62),
                  Y2 = c(273,   267,    329,    329,    386,    401,    399,    350,    274),
                  SD2 = c(107,  85, 141,    126,    94, 101,    65, 65, 58)) 
Y21 = data$Y2/5
SD21 = data$SD2/5
data = cbind(data, Y21, SD21)

ggplot(data=data,aes(x = x ,y=Y1))+
  geom_errorbar(data=data,aes(ymin=Y1-SD1,ymax=Y1+SD1), colour="orange", width = 0.9, size = 1.5, linetype = "solid")+
  geom_point(aes(y=Y1), color = "black")+
  geom_errorbar(data=data,aes(ymin=Y2-SD2,ymax=Y2+SD2),color="blue", width = 0.9, size = 1.5, linetype = "solid")+
  scale_y_continuous("first y axis", sec.axis = sec_axis(Y2~ .*(5)  , name = "second y axis" ))+
  geom_point(aes(y=Y2), color = "black")+
  expand_limits(x = 0, y = 0)

Answer 1

您可以通过

跨多个几何添加图例

为每个geom在aes()内设置color = "label"，其中"label"是每个geom的唯一标签；然后
添加scale_color_manual()（或scale_linetype_manual()等，取决于美学），并将values arg设置为名称对应于geom标签和值的命名向量对应于所需的颜色（或线型，或其他）。

ggplot(data = data,aes(x = x, y = Y1)) +
  geom_errorbar(
    aes(ymin = Y1 - SD1, ymax = Y1 + SD1, color = "Y1"), 
    width = 0.9, 
    size = 1.5
  )+
  geom_point(aes(y = Y1), color = "black") +
  geom_errorbar(
    aes(ymin = Y2 - SD2, ymax = Y2 + SD2, color = "Y2"), 
    width = 0.9, 
    size = 1.5
  ) +
  geom_point(aes(y = Y2), color = "black") +
  scale_y_continuous(
    "first y axis", 
    sec.axis = sec_axis(Y2 ~ .*(5), name = "second y axis")
  ) +
  scale_color_manual("legend title", values = c(Y2 = "blue", Y1 = "orange")) +
  expand_limits(x = 0, y = 0)

Answer 2

通常，如果您发现自己使用手动美学制作了多个相同的几何图形，这表明您应该 pivot your data to long format 并改用具有映射美学的单个几何图形。在您的情况下，这将为您提供图例并简化 ggplot2 规范。

library(tidyverse)

data %>% 
  pivot_longer(Y1:SD2, names_to = c(".value", "yNum"), names_pattern = "(\D+)(\d)") %>% 
  ggplot(aes(x = x, y = Y)) +
  geom_errorbar(
    aes(ymin = Y - SD, ymax = Y + SD, color = yNum), 
    width = 0.9, 
    size = 1.5
  ) +
  geom_point(aes(y = Y), color = "black") +
  scale_y_continuous(
    "first y axis", 
    sec.axis = sec_axis(Y2 ~ .*(5), name = "second y axis")
  ) +
  scale_color_manual(values = c("orange", "blue")) +
  expand_limits(x = 0, y = 0)

不过，如果您确实需要或更喜欢使用单独的 geom，我已经在单独的答案中描述了如何跨多个 geom 生成图例。

将图例添加到基于图的误差条颜色

Adding legend to a plot based error bar color

r

legend

ggplot2