如何阻止 ggrepel 标签在 R/ggplot2 中的 gganimate 帧之间移动？

我想在 ggplot 中的行尾添加标签，避免它们重叠，并避免它们在动画期间移动。

到目前为止，我可以将标签放在正确的位置并使用geom_text，但是标签重叠，或者我可以使用以下方法防止它们重叠geom_text_repel但标签没有出现在我想要的地方，然后一旦情节动画化就跳舞（后一个版本在下面的代码中）。

我认为解决方案可能涉及在 ggplot 中有效创建静态层（p1下面）然后添加一个动画层（p2如下），但似乎不是。

如何在动画 ggplot 中保留绘图常量（即静态）的某些元素？ （在本例中，标签位于行尾。）

此外，与geom_text标签按照我想要的方式显示 - 在每行的末尾，绘图之外 - 但带有geom_text_repel，标签全部移动到绘图区域内。为什么是这样？

这是一些示例数据：

library(dplyr)
library(ggplot2)
library(gganimate)
library(ggrepel)

set.seed(99)

# data
static_data <- data.frame(
  hline_label = c("fixed_label_1", "fixed_label_2", "fixed_label_3", "fixed_label_4", 
                  "fixed_label_5", "fixed_label_6", "fixed_label_7", "fixed_label_8", 
                  "fixed_label_9", "fixed_label_10"), 
  fixed_score = c(2.63, 2.45, 2.13, 2.29, 2.26, 2.34, 2.34, 2.11, 2.26, 2.37))

animated_data <- data.frame(condition = c("a", "b")) %>% 
  slice(rep(1:n(), each = 10)) %>% 
  group_by(condition) %>% 
  mutate(time_point = row_number()) %>% 
  ungroup() %>% 
  mutate(score = runif(20, 2, 3))

这是我用于动画情节的代码：

# colours for use in plot
condition_colours <- c("red", "blue")

# plot static background layer 
p1 <- ggplot(static_data, aes(x = time_point)) +
  scale_x_continuous(breaks = seq(0, 10, by = 2), expand = c(0, 0)) + 
  scale_y_continuous(breaks = seq(2, 3, by = 0.10), limits = c(2, 3), expand = c(0, 0)) + 
  # add horizontal line to show existing scores
  geom_hline(aes(yintercept = fixed_score), alpha = 0.75) + 
  # add fixed labels to the end of lines (off plot)
  geom_text_repel(aes(x = 11, y = fixed_score, label = hline_label), 
                  hjust = 0, size = 4, direction = "y", box.padding = 1.0) +
  coord_cartesian(clip = 'off') +
  guides(col = F) +
  labs(title = "[Title Here]", x = "Time", y = "Mean score") + 
  theme_minimal() + 
  theme(panel.grid.minor = element_blank(),
        plot.margin = margin(5.5, 120, 5.5, 5.5))

# animated layer
p2 <- p1 + 
  geom_point(data = animated_data, 
             aes(x = time_point, y = score, colour = condition, group = condition)) +
  geom_line(data = animated_data, 
            aes(x = time_point, y = score, colour = condition, group = condition), 
            show.legend = FALSE) +
  scale_color_manual(values = condition_colours) + 
  geom_segment(data = animated_data, 
               aes(xend = time_point, yend = score, y = score, colour = condition),
               linetype = 2) + 
  geom_text(data = animated_data, 
            aes(x = max(time_point) + 1, y = score, label = condition, colour = condition), 
            hjust = 0, size = 4) + 
  transition_reveal(time_point) +
  ease_aes('linear') 

# render animation 
animate(p2, nframes = 50, end_pause = 5, height = 1000, width = 1250, res = 120)

供考虑的建议：

1. 具体排斥方向/量/等在geom_text_repel由随机种子决定。你可以set seed到一个恒定值为了在动画的每一帧中获得相同的排斥位置。

2. 我认为排斥的文本不可能超出绘图区域，即使您关闭剪切并指定绘图限制之外的一些排斥范围。该包的全部目的是使文本标签彼此远离，同时保留在绘图区域内。但是，您可以扩大地块面积＆ 使用geom_segment代替geom_hline绘制水平线，使这些线在到达排斥的文本标签之前停止。

3. 由于有更多的几何图层使用animated_data作为他们的数据源，这样会更干净put animated_data以及顶层相关的常见美学映射ggplot() call， 而不是static_data.

这是一个可能的实现。注释中的解释：

p3 <- ggplot(animated_data,
       aes(x = time_point, y = score, colour = condition, group = condition)) +

  # static layers (assuming 11 is the desired ending point)
  geom_segment(data = static_data,
               aes(x = 0, xend = 11, y = fixed_score, yend = fixed_score), 
               inherit.aes = FALSE, colour = "grey25") +
  geom_text_repel(data = static_data,
                  aes(x = 11, y = fixed_score, label = hline_label), 
                  hjust = 0, size = 4, direction = "y", box.padding = 1.0, inherit.aes = FALSE, 
                  seed = 123,           # set a constant random seed
                  xlim = c(11, NA)) +   # specify repel range to be from 11 onwards

  # animated layers (only specify additional aesthetic mappings not mentioned above)
  geom_point() +
  geom_line() +
  geom_segment(aes(xend = time_point, yend = score), linetype = 2) +
  geom_text(aes(x = max(time_point) + 1, label = condition),
            hjust = 0, size = 4) +

  # static aesthetic settings (limits / expand arguments are specified in coordinates
  # rather than scales, margin is no longer specified in theme since it's no longer
  # necessary)
  scale_x_continuous(breaks = seq(0, 10, by = 2)) +
  scale_y_continuous(breaks = seq(2, 3, by = 0.10)) + 
  scale_color_manual(values = condition_colours)  +
  coord_cartesian(xlim = c(0, 13), ylim = c(2, 3), expand = FALSE) +
  guides(col = F) +
  labs(title = "[Title Here]", x = "Time", y = "Mean score") + 
  theme_minimal() + 
  theme(panel.grid.minor = element_blank())  + 

  # animation settings (unchanged)
  transition_reveal(time_point) +
  ease_aes('linear') 

animate(p3, nframes = 50, end_pause = 5, height = 1000, width = 1250, res = 120)