在ggplot线图中叠加点，而不添加图例

Question

给出以下示例数据框：

library(ggplot2)

set.seed(1234)
Site <- c("Blue", "Blue", "Blue", "Blue", "Red", "Red", "Red", "Red", "Green", "Green", "Green", "Green")
Time <- as.POSIXct(c("2019-10-01", "2019-10-10", "2019-11-10", "2019-11-12", "2019-12-12", "2019-12-20", "2019-12-22", "2019-12-25", "2019-12-01", "2019-12-10", "2019-12-12", "2019-12-22"))
DepNum <- jitter(c(1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2))
SS <-c("Start", "Stop", "Start", "Stop", "Start", "Stop", "Start", "Stop", "Start", "Stop", "Start", "Stop")

DF <- data.frame(Site, Time, DepNum, SS)

我想用DepNum变量绘制线形图，但是然后添加第二列（SS）可以着色的点。

ggplot(DF, aes(x = Time, y = DepNum)) + 
  geom_line(aes(color = Site)) +
  geom_point(aes(color = SS))

当我进行以上绘制时，“开始”和“停止”以图例结尾。我想避免“ SS”变量以图例结尾（但保留“ DepNum”图例）。我还想指定点的颜色（又称-“开始”点为绿色，“停止”点为红色）。

研究了这些问题之后，我找到了包含以下内容的答案：geom_point(aes(col = SS), show.legend = FALSE)。但这似乎不起作用：

ggplot(DF, aes(x = Time, y = DepNum)) + 
  geom_line(aes(color = Site)) +
  geom_point(aes(color = SS), show.legend = FALSE)

Answer 1

您要的内容需要具有不同映射的两个不同的色标。这在ggplot2中是不可能的，但可以使用扩展包ggnewscale来完成。它提供了new_scale_color()函数，可让您使用其自己的映射和图例参数定义一个完全独立的第二色标。

library(ggplot2)
library(ggnewscale)

set.seed(1234)
Site <- c("Blue", "Blue", "Blue", "Blue", "Red", "Red", "Red", "Red", "Green", "Green", "Green", "Green")
Time <- as.POSIXct(c("2019-10-01", "2019-10-10", "2019-11-10", "2019-11-12", "2019-12-12", "2019-12-20", "2019-12-22", "2019-12-25", "2019-12-01", "2019-12-10", "2019-12-12", "2019-12-22"))
DepNum <- jitter(c(1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2))
SS <-c("Start", "Stop", "Start", "Stop", "Start", "Stop", "Start", "Stop", "Start", "Stop", "Start", "Stop")

DF <- data.frame(Site, Time, DepNum, SS)

ggplot(DF, aes(x = Time, y = DepNum)) + 
  geom_line(aes(color = Site)) +
  scale_color_manual(
    values = c(Blue = "blue", Red = "red", Green = "green")
  ) +
  new_scale_color() +
  geom_point(aes(color = SS), show.legend = FALSE) +
  scale_color_manual(
    values = c(Start = "green", Stop = "red")
  )

^{由reprex package（v0.3.0）于2019-11-02创建}