如何通过移动点并使用箭头指向原位置解决绘图重叠问题？

你可以借助ggrepel包的排斥算法，手动计算偏移后的点坐标，再用线段/箭头连接偏移点与原位置，替代抖动方案。以下是两种实用实现方式：

方法一：对所有点应用排斥效果 #

直接对全部数据点计算偏移位置，绘制偏移点并添加指向原位置的箭头：

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

# 初始化排斥位置参数，可调整force/point.padding控制排斥力度
repel_pos <- position_repel(
  point.padding = unit(0.5, "lines"),
  force = 1,
  direction = "both"
)

# 计算所有点的偏移后坐标
mpg_repel <- repel_pos$compute_layer(
  data = mpg,
  params = list(),
  layout = ggplot2:::Layout$new(ggplot(mpg, aes(displ, cty)))
) %>%
  rename(displ_repel = x, cty_repel = y) %>%
  bind_cols(mpg)

# 绘制图形
ggplot() +
  # 箭头：从偏移点指向原位置
  geom_segment(
    data = mpg_repel,
    aes(x = displ_repel, y = cty_repel, xend = displ, yend = cty),
    color = "gray50",
    arrow = arrow(length = unit(0.1, "cm"))
  ) +
  # 偏移后的主体点
  geom_point(
    data = mpg_repel,
    aes(displ_repel, cty_repel, colour = drv, fill = drv),
    shape = 21, size = 3
  ) +
  # 可选：原位置标记，增强可读性
  geom_point(
    data = mpg,
    aes(displ, cty),
    shape = 20, size = 1, color = "black"
  ) +
  scale_color_manual(values = c("4" = "red", "f" = "blue", "r" = "green")) +
  scale_fill_manual(values = c("4" = "pink", "f" = "lightblue", "r" = "lightgreen")) +
  theme_bw()

方法二：仅处理重叠点（减少杂乱） #

如果只想对真正重叠的点做偏移处理，先筛选重叠数据再应用排斥：

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

# 筛选出存在重叠的点（同一坐标出现多次）
overlap_points <- mpg %>%
  count(displ, cty) %>%
  filter(n > 1) %>%
  select(-n) %>%
  inner_join(mpg, by = c("displ", "cty"))

# 初始化排斥位置参数
repel_pos <- position_repel(
  point.padding = unit(0.5, "lines"),
  force = 1.5,
  direction = "both"
)

# 计算重叠点的偏移坐标
overlap_repel <- repel_pos$compute_layer(
  data = overlap_points,
  params = list(),
  layout = ggplot2:::Layout$new(ggplot(overlap_points, aes(displ, cty)))
) %>%
  rename(displ_repel = x, cty_repel = y) %>%
  bind_cols(overlap_points)

# 绘制图形：非重叠点直接绘制原位置，重叠点做偏移+箭头
ggplot() +
  # 非重叠点
  geom_point(
    data = anti_join(mpg, overlap_points, by = c("displ", "cty")),
    aes(displ, cty, colour = drv, fill = drv),
    shape = 21, size = 3
  ) +
  # 重叠点的箭头
  geom_segment(
    data = overlap_repel,
    aes(x = displ_repel, y = cty_repel, xend = displ, yend = cty),
    color = "gray50",
    arrow = arrow(length = unit(0.1, "cm"))
  ) +
  # 重叠点的偏移点
  geom_point(
    data = overlap_repel,
    aes(displ_repel, cty_repel, colour = drv, fill = drv),
    shape = 21, size = 3
  ) +
  # 可选：重叠点原位置标记
  geom_point(
    data = overlap_points,
    aes(displ, cty),
    shape = 20, size = 1, color = "black"
  ) +
  scale_color_manual(values = c("4" = "red", "f" = "blue", "r" = "green")) +
  scale_fill_manual(values = c("4" = "pink", "f" = "lightblue", "r" = "lightgreen")) +
  theme_bw()

调整技巧 #

• 修改position_repel的force参数：数值越大，点之间的排斥力度越强
• 调整point.padding：控制点与边界的最小间距
• 通过arrow()函数自定义箭头样式，比如修改length、type参数

内容的提问来源于stack exchange，提问作者Alex Krohn