为什么我的图例没有出现在图表旁边？

Question

我在一个散点图中有两个不同的数据集，图例中的 prediction2020_bounds 需要为蓝色，图例中的 median2020 需要为红色。 这是我的代码：

  ggplot() + 
      
    # Points without corona
    geom_line(data=prediction2020_bounds, aes(x = Date, y = lwr), colour = "blue", linetype = "solid") +
    geom_line(data=prediction2020_bounds, aes(x = Date, y = upr), colour = "blue", linetype = "solid") +
    geom_ribbon(data=prediction2020_bounds, aes(x = Date, ymin = lwr, ymax = upr), alpha=.4) +
    labs(x = "Date", y = "Median Daily Price", title = "Daily Median Price", colour = "Legend Title\n") +
    scale_x_date(date_breaks="1 month", date_labels="%Y %m") +
    scale_colour_manual(labels = c("prediction2020_bounds", "median2020"), values = c(prediction2020_bounds, median2020)) +
    theme_bw() +
    geom_point(data=prediction2020_bounds, aes(x=Date, y=Price),fill="blue",
          colour="darkblue", size=1) +
    
    
    #Points with corona 2020 year
    geom_point(data=median2020, aes(x=Date, y=Price), fill="red",
            colour="red", size=1) 

Answer 1

下次请考虑包含一些可重复的示例，以便其他人更容易支持您找到一个好的答案；）

要在ggplot2 中显示图例，您需要将mapping 参数内的colour 或fill 映射为aes()，而不是您在问题中所做的事情。下面的代码是实现你想要做的事情的一种方式。

我还根据个人喜好重新格式化代码，其中绘图的配置scales、labels、theme 都在底部，而 geom 在顶部 @987654332 @ 命令。这只是个人喜好。

希望这能帮助你更好地理解ggplot2中的传说。

color_names <- c("prediction 2020 bounds", "median 2020")
color_values <- c("blue", "red")
names(color_values) <- color_names
ggplot() + 
  
  # Points without corona
  geom_line(data=prediction2020_bounds, aes(x = Date, y = lwr,
    # assign the colour to the same name as blue value of color_values
    colour = "prediction 2020 bounds"),  linetype = "solid") +
  geom_line(data=prediction2020_bounds, aes(x = Date, y = upr,
    # assign the colour to the same name as blue value of color_values
    colour = "prediction 2020 bounds"), linetype = "solid") +
  geom_ribbon(data=prediction2020_bounds, aes(x = Date, ymin = lwr, ymax = upr),
    alpha=.4) +
  geom_point(data=prediction2020_bounds, aes(x=Date, y=Price,
    # assign the fill to the same name as blue value of color_values
    fill="prediction 2020 bounds"), 
    colour="darkblue", size=1) +

  #Points with corona 2020 year
  geom_point(data=median2020, aes(x=Date, y=Price, 
    # assign the colour to the same name as red value of color_values
    fill="median 2020"),
    colour="median 2020", size=1) +
  
  # plot configuration scales, theme, etc...
  labs(x = "Date", y = "Median Daily Price",
    title = "Daily Median Price", colour = "Legend Title\n") +
  scale_x_date(date_breaks="1 month", date_labels="%Y %m") +
  scale_colour_manual(values = color_values) +
  scale_fill_manual(values = color_values) +
  theme_bw()

除此之外，您还可以在哪里使用theme(legend.position = [position] [position]可以

• none: 不显示图例
• left/right/botom/top：对应位置与主地块区域相关

我发现这篇文章内容丰富，解释透彻 https://aosmith.rbind.io/2018/07/19/manual-legends-ggplot2/