我们如何在单个图表中使用多个geom_smooth？

Question

我想在单个ggplot2图表中使用多个geom_smooth图层。当我尝试这样做时，配色方案搞砸了。这是一个展示正在发生的事情的例子。

我们构建一个我们想要可视化的简单数据帧。

df = data.frame(x = c("a", "b", "c"),
             y1 = seq(1, 3),
             y1_upr = seq(2, 4),
             y1_lwr = seq(0, 2),
             y2 = seq(2, 4),
             y2_upr = seq(2.5, 4.5),
             y2_lwr = seq(1.5, 3.5))

我们可以轻松地将y1和y2可视化。

plot_obj = ggplot(data = df, aes(x = x, group = 1)) + 
  geom_line(aes(y = y1, colour = "y1")) + 
  geom_line(aes(y = y2, colour = "y2")) +     
  scale_colour_manual("", breaks = c("y1", "y2"), values = c("blue", "red"))
plot_obj

如果我们添加一个geom_smooth，行为仍然符合预期。

plot_obj + 
  geom_smooth(aes(y = y1, ymin = y1_lwr, ymax = y1_upr), stat="identity", fill="blue", alpha=0.2)

最后，我们添加第二个geom_smooth图层。

plot_obj + 
  geom_smooth(aes(y = y1, ymin = y1_lwr, ymax = y1_upr), stat="identity", fill="blue", alpha=0.2) + 
  geom_smooth(aes(y = y2, ymin = y2_lwr, ymax = y2_upr), stat="identity", fill="red", alpha=0.2)

请注意，最后一个图表中的顶行不再是红色。为什么会发生这种情况？如何解决？谢谢！

Answer 1

我可能会更接近这个：

library(dplyr)
df1 <- df %>%
    select(x,contains("y1")) %>%
    rename(y = y1, y_upr = y1_upr, y_lwr = y1_lwr) %>%
    mutate(grp = "y1")
df2 <- df %>%
    select(x,contains("y2")) %>%
    rename(y = y2, y_upr = y2_upr, y_lwr = y2_lwr) %>%
    mutate(grp = "y2")
df_all <- bind_rows(df1, df2)

ggplot(df_all,aes(x = x, y = y, ymin = y_lwr, ymax = y_upr, group = grp)) +
    geom_line(aes(color = grp)) + 
    geom_ribbon(aes(fill = grp), alpha = 0.2)

Answer 2

当然，重塑数据集会使事情变得更容易，并且是推荐的方法。但是，如果您想继续使用单独的图层：

由于您尚未为color映射geom_smooth，因此它会使用默认颜色为蓝色来绘制平滑的线条。如果您只想要功能区，请改用geom_ribbon。

ggplot(data = df, aes(x = x, group = 1)) + 
    geom_line(aes(y = y1, colour = "y1")) + 
    geom_line(aes(y = y2, colour = "y2")) +     
    scale_colour_manual("", breaks = c("y1", "y2"), values = c("blue", "red")) +
    geom_ribbon(aes(ymin = y1_lwr, ymax = y1_upr), stat="identity", fill="blue", alpha=0.2) + 
    geom_ribbon(aes(ymin = y2_lwr, ymax = y2_upr), stat="identity", fill="red", alpha=0.2)

否则，您需要为aes中的每个平滑图层映射颜色，或者在aes之外手动将其设置为红色和蓝色或NA。

ggplot(data = df, aes(x = x, group = 1)) + 
    geom_line(aes(y = y1, colour = "y1")) + 
    geom_line(aes(y = y2, colour = "y2")) +     
    scale_colour_manual("", breaks = c("y1", "y2"), values = c("blue", "red")) +
    geom_smooth(aes(y = y1, ymin = y1_lwr, ymax = y1_upr, colour = "y1"), 
              stat="identity", fill="blue", alpha=0.2) + 
    geom_smooth(aes(y = y2, ymin = y2_lwr, ymax = y2_upr, colour = "y2"), 
              stat="identity", fill="red", alpha=0.2)