如何停止 ggrepel 标签在 R/ggplot2 中的 gganimate 帧之间移动？

Question

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四处移动。

到目前为止，我可以将标签放在正确的位置并使用geom_text 将它们保持为静态，但标签重叠，或者我可以使用geom_text_repel 防止它们重叠，但标签不会出现在我希望它们出现的位置并且然后在情节动画化后跳舞（后一个版本在下面的代码中）。

我认为一个解决方案可能涉及在 ggplot 中有效地创建一个静态层（下面的p1）然后添加一个动画层（下面的p2），但似乎不是。

如何在动画 ggplot 中保存绘图常量（即静态）的某些元素？ （在这种情况下，行尾的标签。）

此外，使用geom_text，标签按我想要的方式显示——在每行的末尾，在绘图之外——但使用geom_text_repel，标签都在绘图区域内移动。为什么是这样？

以下是一些示例数据：

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)

Answer 1

供考虑的建议：

1. geom_text_repel中具体的排斥方向/数量/等由随机种子决定。您可以将seed 设置为一个常数值，以便在每一帧动画中获得相同的排斥位置。

2. 我认为被排斥的文本不可能超出绘图区域，即使您关闭剪辑并在绘图限制之外指定一些排斥范围也是如此。该软件包的重点是使文本标签彼此远离，同时保持在绘图区域内。但是，您可以扩展绘图区域并使用geom_segment 而不是geom_hline 来绘制水平线，这样这些线就会在它们到达被排斥的文本标签之前停止。

   李>

3. 由于使用animated_data 作为数据源的几何图层较多，因此将animated_data 和相关的常见美学映射放在顶层ggplot() 调用中会更简洁 ，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)