r - 如何改变 "position_dodge"一个点而不是 ggplot2 系列中的其他点

Question

问题:我的数据集有一个共享基线(时间点 1)和 2 个重复测量。后续点在 2 个不同的条件下重复(即交叉)。绘图时，结果、误差线和数据点重叠。

library(tidyverse)
set.seed(11)
df_test <-
  tibble(group = factor(rep(c("A", "B"), each = 3)),
         timepoint  = factor(rep(1:3, 2)),
         y = c(0, rnorm(2, mean = 0, sd = .2), 0, rnorm(2, mean = .7, sd = 0.35))) %>% 
  mutate(ymax = y + .2,
         ymin = y - .2)

# plot_nododge <- 
df_test %>% 
  ggplot(aes(timepoint, y,
             group = group,
             shape = group,
             fill = group)) +
  geom_linerange(linetype = 1,
                 aes(ymin = ymin,
                     ymax = ymax)) +
  geom_point() +
  geom_line()

使用 position_dodge() 的解决方案: 该解决方案修复了重叠，但“基线”点实际上是一个单独的度量。我希望这是一个单一的点，以避免混淆，但仍然避开后续点。

有没有我缺少的简单解决方案？

我想为每个点使用自定义闪避(例如 scale_position_dodge_identity)，但位置不被接受为美学。

# plot1 <- 
  df_test %>% 
  ggplot(aes(timepoint, y,
             group = group,
             shape = group,
             fill = group)) +
  geom_linerange(linetype = 1,
                 position = position_dodge(.2),
                 aes(ymin = ymin,
                     ymax = ymax)) +
  geom_point(position = position_dodge(.2)) +
  geom_line(position = position_dodge(.2))

解决与扩展*也许将来会开发出更好的东西，但现在手动调整位置似乎是最好的。由于点的形状和颜色也应该反射(reflect)不同的“基线”度量，并且 x 轴应该有很好的标签，所以我进行了编辑以显示更多的收尾工作。

df_test %>% 
  mutate(shape_var = case_when(timepoint == 1 ~ 22,
                               group == "A" ~ 21,
                               group == "B" ~ 24),
         fill_var = case_when(timepoint == 1 ~ "black",
                              group == "A" ~ "red",
                              group == "B" ~ "blue"),
         timepoint2 = as.numeric(as.character(timepoint)),
         timepoint2 = timepoint2 + 0.05*(timepoint2 > 1 & group == "B"),
         timepoint2 = timepoint2 - 0.05*(timepoint2 > 1 & group == "A")) %>% 
  ggplot(aes(timepoint2, y,
             group = group,
             shape = shape_var,
             fill = fill_var)) +
  geom_linerange(aes(ymin = ymin,
                     ymax = ymax)) +
  geom_line() +
  geom_point(size = 2) +
  scale_x_continuous(breaks = 1:3, # limit to selected time points
                     labels = c("Baseline", "time 1", "time 2"), # label like a discrete scale
                     limits =  c(.75, 3.25)) + # give it some room
  scale_shape_identity(guide = "legend",
                       name = "Treatment",
                       breaks = c(21, 24), # Defines legend order too; only label the treatment groups
                       labels = c("A", "B" )) + # this part is tricky - could easily reverse them
  scale_fill_identity(guide = "legend",
                      name = "Treatment",
                      breaks = c("red", "blue"),# Defines legend order too; only label the treatment groups
                      labels = c("A", "B" )) +  # this part is tricky - could easily reverse them
  labs(x=NULL)

^{由 reprex package 创建于 2021-09-19 (v2.0.1)}

Answer 1

经过一些实验，我找到了一个非常好的方法来做到这一点。似乎您可以使用 position_dodge2(width = c(...)) 来指定单独的闪避宽度。

对于您的示例，指定 width = c(0.000001, 0.2, 0.2):

df_test %>% 
  ggplot(aes(timepoint, y, group = group, shape = group, fill = group)) +
  geom_linerange(linetype = 1, position = position_dodge2(width = c(0.000001, 0.2, 0.2)), aes(ymin = ymin, ymax = ymax)) +
  geom_point(position = position_dodge2(width = c(0.000001, 0.2, 0.2))) +
  geom_line(position = position_dodge2(width = c(0.000001, 0.2, 0.2)))

最初，我尝试设置 width = c(0, 0.2, 0.2)，但没有按预期运行:

?position_dodge 没有明确解释使用一串值作为闪避宽度，所以我不知道为什么当您使用零作为宽度时它不起作用。 0.000001 的值“足够接近”零，您无法通过查看该图来判断，因此希望这就足够了。