ggplot2：如何通过多个变量为图表着色

我相当确定我在某处看到了这个问题的解决方案，但由于我无法找到它，这就是我的问题。

我有一些由多个变量标识的时间序列数据，我希望能够使用多个变量来绘制图表并区分颜色ggplot2.

样本数据：

date <- c("2016-04-01 UTC", "2016-05-01 UTC", "2016-06-01 UTC", "2016-04-01 UTC",
          "2016-05-01 UTC", "2016-06-01 UTC", "2016-04-01 UTC", "2016-05-01 UTC",
          "2016-06-01 UTC", "2016-04-01 UTC")
temp <- c(80.24018,  85.88911, 104.23125,  85.13571,  91.21129, 104.88333,  97.81116,
          107.40484, 121.03958,  87.91830)
id <- c("A","A","A","A","A","B","B","B","B","B")
location <- c("N","S","S","N","N","S","N","S","N","S")

df <- data.frame(date,temp,id,location)

我在绘图方面的尝试

library(ggplot2)

ggplot(df) + 
  geom_line(aes(x=date,y=temp,colour=factor(location), group=interaction(location,id)))

使用此代码仅按位置着色。我想根据位置和 ID 对线条进行着色。

两种选择：

library(ggplot2)

df <- data.frame(date = c("2016-04-01 UTC", "2016-05-01 UTC", "2016-06-01 UTC", "2016-04-01 UTC", "2016-05-01 UTC", "2016-06-01 UTC", "2016-04-01 UTC", "2016-05-01 UTC", "2016-06-01 UTC", "2016-04-01 UTC"),
                 temp = c(80.24018,  85.88911, 104.23125,  85.13571,  91.21129, 104.88333,  97.81116, 107.40484, 121.03958,  87.91830),
                 id = c("A","A","A","A","A","B","B","B","B","B"),
                 location = c("N","S","S","N","N","S","N","S","N","S"))

df$date <- as.Date(df$date)    # parse dates to get a nicer x-axis

Map id给颜色和location到线型：

ggplot(df, aes(date, temp, color = id, linetype = location)) + geom_path()

...或将所有交互绘制为不同的颜色：

ggplot(df, aes(date, temp, color = id:location)) + geom_path()