R ggplot2 geom_text调用position_dodge时部分标签重叠问题

问题表现 #

• 绘图目标：呈现环境可持续性、经济可持续性、社会可持续性三个变量随企业类型的变化规律
• 初始操作：为geom_text图层设置position = position_dodge参数，尝试错开不同分组的数值标签
• 异常现象：环境可持续性（绿色）、社会可持续性（蓝色）的标签已正常错开，经济可持续性（黄色）对应的数值标签与同组点形重叠，排布异常
  

原始复现代码 #

ggplot(DS, aes(x=Valore, y=Azienda, fill=Sostenibilità_effettiva, colour=Sostenibilità_effettiva))
+ geom_point(aes(shape=Sostenibilità_effettiva, color=Sostenibilità_effettiva),stat = "identity", size=1.5) 
+ theme(strip.text = element_text(size = 5, family="Helvetica"), axis.title=element_text(size=7, family="Helvetica", face="bold"), axis.text.x=element_text(size=6, family="Helvetica"), axis.text.y=element_text(size=6, family="Helvetica"), legend.title=element_text(size=7, family="Helvetica"), legend.text=element_text(size=6, family="Helvetica"), panel.background=element_blank(), legend.position = "top", axis.line=element_line(color="black"), axis.ticks=element_line(color="black"), panel.grid.major.y = element_line(color = "black", size = 0.25, linetype = 3)) 
+ geom_vline(data=media_importanza, aes(xintercept=Mean, color=Sostenibilità_effettiva), linetype = "dashed", size=0.5) + scale_color_manual(values=c("#4cb71e", "#fabd01", "#197bd3"))
+ geom_text(data = DS, aes(label=Valore),color="black", position=position_dodge(width = 1), hjust=.5, size=2)

问题原因 #

出现该问题的核心原因是图层间位置偏移参数不统一：仅给geom_text图层设置了宽度为1的dodge偏移，但geom_point图层未设置匹配的位置偏移参数，ggplot2对不同图层默认的分组偏移量计算逻辑存在差异，最终导致部分分组的点和标签位置错位重叠。

修复方案 #

• 给geom_point图层添加与geom_text完全一致的position = position_dodge(width = 1)参数，保证两个图层的分组偏移量完全匹配
• 若修复后标签仍与点存在轻微剐蹭，可适当调整geom_text的hjust参数，或给标签增加0.02左右的x轴微小偏移拉开距离

修复后完整代码 #

ggplot(DS, aes(x=Valore, y=Azienda, fill=Sostenibilità_effettiva, colour=Sostenibilità_effettiva)) +
  geom_point(
    aes(shape=Sostenibilità_effettiva, color=Sostenibilità_effettiva),
    stat = "identity", 
    size=1.5,
    # 新增与text层一致的dodge偏移参数
    position = position_dodge(width = 1)
  ) + 
  theme(
    strip.text = element_text(size = 5, family="Helvetica"), 
    axis.title=element_text(size=7, family="Helvetica", face="bold"), 
    axis.text.x=element_text(size=6, family="Helvetica"), 
    axis.text.y=element_text(size=6, family="Helvetica"), 
    legend.title=element_text(size=7, family="Helvetica"), 
    legend.text=element_text(size=6, family="Helvetica"), 
    panel.background=element_blank(), 
    legend.position = "top", 
    axis.line=element_line(color="black"), 
    axis.ticks=element_line(color="black"), 
    panel.grid.major.y = element_line(color = "black", size = 0.25, linetype = 3)
  ) +
  geom_vline(
    data=media_importanza, 
    aes(xintercept=Mean, color=Sostenibilità_effettiva), 
    linetype = "dashed", 
    size=0.5
  ) + 
  scale_color_manual(values=c("#4cb71e", "#fabd01", "#197bd3")) +
  geom_text(
    data = DS, 
    aes(label=Valore),
    color="black", 
    position=position_dodge(width = 1), 
    hjust=.5, 
    size=2
  )

内容的提问来源于stack exchange，提问作者Alberto Bertossi