ggplot进阶之图例系统

library(tidyverse)

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✔ lubridate 1.9.3     ✔ tidyr     1.3.1
✔ purrr     1.0.2     

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mpg %>% 
  ggplot(aes(x = displ, y = hwy, color = factor(cyl)))+
  geom_point()

如果想调整图例的样式，可以使用guides()函数，用法类似theme函数, 具体参数为：

• 要么是字符串 (i.e. "color = colorbar" or "color = legend"),

• 要么是特定的函数 (i.e. color = guide_colourbar() or color = guide_legend())

以下 guides() 函数族用于控制图例的外观

• guide_colorbar(): continuous colors

• guide_legend(): discrete values (shapes, colors)

• guide_axis(): control axis text/spacing, add a secondary axis

• guide_bins(): creates “bins” of values in the legend

• guide_colorsteps(): makes colorbar discrete

2 案例详解

mpg %>% 
  ggplot(aes(x = displ, y = hwy, color = factor(cyl)))+
  geom_point()+
  ggtitle("This is a title")+
  labs(x = "x_displ", y = "y_hwy")+
  guides(color = "legend")

mpg %>%
  ggplot(aes(x = displ, y = hwy, color = factor(cyl))) +
  geom_point() +
  ggtitle("This is my title") +
  labs(x = "x_displ", y = "y_hwy") +
  guides(color = guide_legend(title = "my title",
                              label.hjust = 1))

mpg %>%
  ggplot(aes(x = displ, y = hwy, color = factor(cyl))) +
  geom_point() +
  ggtitle("This is my title")  +
  labs(x = "x_displ", y = "y_hwy") +
  guides(color = guide_legend(ncol = 4, 
                              title = "my title"))

mpg %>%
  ggplot() + 
  geom_jitter(aes(x = cty, y = hwy, color = class),
              key_glyph = draw_key_pointrange)+
  guides(color = guide_legend(nrow = 1))+
  theme(legend.position = "top",
        axis.text = element_text(face = "italic", color = "navy"),
        plot.background = element_rect(fill = "#a0d1f2"),
        panel.background = element_blank(),
        panel.grid = element_line(linetype = "dotdash"))

mpg %>%
  ggplot(aes(x = displ, y = hwy, color = factor(cyl))) +
  geom_point() +
  ggtitle("This is my title")  +
  labs(x = "x_displ", y = "y_hwy") +
  guides(color = guide_legend(title = "title is too high",
                              title.position = "top",
                              title.vjust = 5,
                              label.position = "left",
                              label.hjust = 1,
                              label.theme = element_text(size = 15, angle = 0,
                                                         face = "italic",color = "red"),
                              keywidth = 5,
                              reverse = TRUE))

3 删除其中一个图例

guides(color = "none)

guides(color = guide_none())

mpg %>% 
  ggplot(aes(x = displ, y = hwy, color = class, size = cyl))+
  geom_point()

比如，我们想删除size这个图例，那么需要这样做

mpg %>% 
  ggplot(aes(x = displ, y = hwy, color = class, size = cyl))+
  geom_point()+
  guides(color = guide_legend("type"),  # keep
         size = "none")                 # remove

mpg %>% 
  ggplot(aes(x = displ, y = hwy, color = class, size = cyl))+
  geom_point()+
  guides(color = guide_legend("class"),  # keep
         size = "none")                 # remove

或者

mpg %>%
  ggplot(aes(x = displ, y = hwy, color = class, size = cyl)) +
  geom_point() +
  guides(color = guide_legend("type"),
         size = guide_none())

4 合并图例

library(tidyverse)
library(palmerpenguins)

penguins %>% 
  ggplot(aes(x = bill_length_mm, y = bill_depth_mm,
             color = body_mass_g, size = body_mass_g))+
  geom_point(alpha = 0.6)+
  scale_color_viridis_c()

Warning message:
“Removed 2 rows containing missing values or values outside the scale range (`geom_point()`).”

这里color 和 size 都使用了body_mass_g映射，我们可以将两者合并

penguins %>% 
  ggplot(aes(x = bill_length_mm, y = bill_depth_mm,
             color = body_mass_g, size = body_mass_g))+
  geom_point(alpha = 0.6)+
  scale_color_viridis_c()+
  guides(color = guide_legend())

Warning message:
“Removed 2 rows containing missing values or values outside the scale range (`geom_point()`).”

更直观的方法

penguins %>% 
  ggplot(aes(x = bill_length_mm, y = bill_depth_mm,
             color = body_mass_g, size = body_mass_g))+
  geom_point(alpha = 0.6)+
  scale_color_viridis_c()+
  guides(color = guide_legend(),
         size  = guide_legend())

Warning message:
“Removed 2 rows containing missing values or values outside the scale range (`geom_point()`).”

或者

penguins %>% 
  ggplot(aes(x = bill_length_mm, y = bill_depth_mm,
             color = body_mass_g, size = body_mass_g))+
  geom_point(alpha = 0.6)+
  scale_color_viridis_c()+
  guides(color = guide_legend("title"),
         size  = guide_legend("title"))

Warning message:
“Removed 2 rows containing missing values or values outside the scale range (`geom_point()`).”

最省力的是

penguins %>% 
  ggplot(aes(x = bill_length_mm, y = bill_depth_mm,
             color = body_mass_g, size = body_mass_g))+
  geom_point(alpha = 0.6)+
  scale_color_viridis_c(guide = "legend")

Warning message:
“Removed 2 rows containing missing values or values outside the scale range (`geom_point()`).”

mtcars %>%
  as_tibble() %>%
  ggplot(aes(x = wt, y = mpg, shape = factor(vs), color = hp)) +
  geom_point(size = 3) +
  colorspace::scale_color_continuous_sequential(palette = "Dark Mint") +
  scale_shape_discrete(labels = c("V-shaped", "Straight")) +
  labs(
    x = "Weight (1000 lbs)", y = "Miles per gallon",
    title = "Motor Trend Car Road Tests",
    shape = "Engine", color = "Horsepower"
  ) +
  theme(
    text = element_text(size = 18, color = "white"),
    rect = element_rect(fill = "black"),
    panel.background = element_rect(fill = "black"),
    legend.key = element_rect(fill = "black"),
    axis.text = element_text(color = "white"),
    plot.title.position = "plot",
    plot.margin = margin(10, 10, 10, 10)
  ) +
  guides(
    shape =
      guide_legend(override.aes = list(color = "white"))
  )