ggplot2修改图例标题时出现重复图例问题求助

问题原因 #

你同时在aes()里把member_type映射给了fill（填充色）和color（边框色）两个属性。一开始ggplot会因为两个属性映射的是同一个变量，自动合并图例；但当你只在labs()里修改fill的标题时，两个图例的标题不一致，ggplot就会把它们拆成两个独立的图例。

两种解决方案 #

方案1：同时设置fill和color的标题，让它们一致

在labs()里同时指定fill和color的标题为同一个内容，ggplot就会自动合并图例：

data_2023_2 %>% 
  group_by(rideable_type, member_type) %>%
  dplyr::summarize(total_trips = n()) %>% 
  ggplot(aes(x=rideable_type, y=total_trips, fill=member_type, color=member_type)) +
  geom_bar(stat='identity', position = position_dodge2(preserve = "single", padding = 0.1)) +
  geom_text(aes(label = total_trips), position = position_dodge2(preserve = "single", width = 0.9, padding = 0.1), vjust=1.5, colour="white") +
  scale_fill_manual(values=c("darkorchid","darkseagreen")) +
  scale_color_manual(values=c("darkorchid","darkseagreen")) +
  theme_bw()+
  labs(title="Number of Trips by Bike Type", x="Bicycle Type", y="Number of Rides", fill="Member Type", color="Member Type")

方案2：直接隐藏color的图例（更简洁）

因为你设置的填充色和边框色完全一样，其实不需要保留color的图例，用guides()函数把它隐藏即可：

data_2023_2 %>% 
  group_by(rideable_type, member_type) %>%
  dplyr::summarize(total_trips = n()) %>% 
  ggplot(aes(x=rideable_type, y=total_trips, fill=member_type, color=member_type)) +
  geom_bar(stat='identity', position = position_dodge2(preserve = "single", padding = 0.1)) +
  geom_text(aes(label = total_trips), position = position_dodge2(preserve = "single", width = 0.9, padding = 0.1), vjust=1.5, colour="white") +
  scale_fill_manual(values=c("darkorchid","darkseagreen")) +
  scale_color_manual(values=c("darkorchid","darkseagreen")) +
  theme_bw()+
  labs(title="Number of Trips by Bike Type", x="Bicycle Type", y="Number of Rides", fill="Member Type") +
  guides(color = "none") # 隐藏color对应的图例

内容的提问来源于stack exchange，提问作者aoao