我有一个包含两个分类变量和一个数值变量的数据表。
这是生成示例数据的代码：
data <- data.frame(system = rep(c("X","Y","Z"), 10),
                   region = rep(letters[1:5], 6),
                   value = rnorm(60, 500, 300))
现在我想绘制值的系统-区域均值，并将系统均值叠加在系统-区域均值上。
以下是用于绘图数据和第一个绘图的代码：
plot_data <- data %>%
  mutate(system = factor(system), region = factor(region)) %>%
  group_by(system, region) %>%
  summarise(avg = mean(value), .groups = "drop") %>%
  left_join(y = data %>% group_by(system) %>% summarise(avg = mean(value), .groups = "drop"), by = "system", suffix = c("", "_all")) %>%
  mutate(point_type = ifelse(avg_all > avg, "above", "in"))
ggplot(plot_data, aes(x = region, y = avg, fill = system)) +
  geom_col(position = "dodge") +
  geom_point(aes(y = avg_all), shape = 21, position = position_dodge(width = 0.9))
但是现在，如果我想要为geom_point添加颜色美观，就像这样：
ggplot(plot_data, aes(x = region, y = avg, fill = system)) +
  geom_col(position = "dodge") +
  geom_point(aes(y = avg_all, color = point_type), shape = 21, position = position_dodge(width = 0.9))
那么图形不再以与列相同的顺序排列点在position.dodge内。请注意，在区域'b'中，绿色和蓝色的点/条形物不对齐，在区域'd'中，红色和绿色的点/条形物不对齐，在区域'e'中，红色、绿色和蓝色的点/条形物不对齐。我无法弄清楚原因。不对齐不是系统性的，但我尝试了position = position.dodge2(reverse = T)，也没有解决问题。

library(ggplot2)
ggplot(plot_data, aes(x = region, y = avg, fill = system)) +
  geom_col(position = "dodge") +
  geom_point(aes(y = avg_all, color = point_type, group = system),
    shape = 21, position = position_dodge(width = 0.9)
  )

<details>
<summary>英文:</summary>
The issue is that by adding the `color` aes you changed the grouping of the data used for `geom_point`. To fix that you have to use the `group` aes, to tell `ggplot2` that you want the points grouped and dodged by `system`.

[![enter image description here][1]][1]
  [1]: https://i.stack.imgur.com/CAaAP.png
</details>
# 答案2
**得分**: 2
我有点迟到，已经有一个使用 `group` 的答案了。我建议在第一个 `aes` 中使用 `group = system`，这样它将在各个几何图层之间共享更有意义。
另一个选项（虽然不会产生完全相同的图表，我认为这不是一个好的解决方案）是在第一个 `aes` 中定义 `color`，然后在 `geom_col` 中覆盖它。
``` r
ggplot(plot_data, aes(x = region, y = avg, fill = system, color = point_type)) +
  geom_col(position = "dodge", color = "white", size = 0.1) +
  geom_point(aes(y = avg_all), 
             shape = 21, position = position_dodge(width = 0.9))