ggplot2：组合组、颜色和线型答案

【问题标题】：ggplot2: Combining group, color and linetypeggplot2：组合组、颜色和线型
【发布时间】：2018-12-02 15:36:12
【问题描述】：

我有一个包含 3 个因子（condition、measure 和 time）的数据库，并希望使用 x 轴、颜色/组和线型来绘制它们。

例如，我的数据如下所示：

DT <- data.frame(condition = rep(c("control", "experimental"), each = 4),
                 measure = rep(c("A", "A", "B", "B"), 2),
                 time = rep(c("pre-test", "post-test"), 4),
                 score = 1:8)

> DT
     condition measure      time score
1      control       A  pre-test     1
2      control       A post-test     2
3      control       B  pre-test     3
4      control       B post-test     4
5 experimental       A  pre-test     5
6 experimental       A post-test     6
7 experimental       B  pre-test     7
8 experimental       B post-test     8

我的目标是画出这样的图表：

我试过了：

ggplot(DT, aes(time, score, group = measure, color = measure, linetype = condition)) +
    geom_line() +
    geom_point()

但它返回此错误：

Error: geom_path: If you are using dotted or dashed lines, colour, size and linetype must be constant over the line

我错过了什么？

【问题讨论】：

标签： r ggplot2

【解决方案1】：

你想用

ggplot(DT, aes(time, score, group = interaction(measure, condition), 
               color = measure, linetype = condition)) +
  geom_line() + geom_point()

因为实际分组不仅是measure，还有condition。当单独按measure 分组时，我猜它要求的是平行四边形而不是直线。

【讨论】：

【解决方案2】：

data.frame(
  condition = rep(c("control", "experimental"), each = 4),
  measure = rep(c("A", "A", "B", "B"), 2),
  time = rep(c("pre-test", "post-test"), 4),
  score = 1:8
) -> DT

DT_wide <- tidyr::spread(DT, time, score)

ggplot() +
  geom_segment(
    data = DT_wide,
    aes(
      x = "pre-test", xend = "post-test", 
      y = `pre-test`, yend = `post-test`,
      color = measure, 
      linetype = condition
    )
  ) +
  geom_point(
    data = DT,
    aes(time, score, color = measure)
  )

【讨论】：