R ggplot多分组柱状图顶部数据标签显示异常问题求助

问题根因 #

标签错位是两个原因导致的：

1. 原代码中x轴映射为连续日期类型，两个日期间隔接近3个月，ggplot默认的分组闪避宽度基于x轴数值间隔计算，手动设置的0.9闪避宽度和柱子实际闪避宽度不匹配
2. 没有明确给geom_bar设置统一的闪避宽度，导致文本和柱子的闪避规则不一致

修正方案 #

将x轴转为离散因子类型（更符合两个季度对比的展示场景），同时统一柱子和文本的闪避宽度，修正后完整代码如下：

# 加载依赖包
library(ggplot2)
library(dplyr)

# 数据构造逻辑保持不变
Date <- as.Date(c("2020-10-01","2020-10-01","2020-10-01","2020-10-01",
                  "2020-10-01","2020-10-01","2020-10-01","2020-10-01","2020-10-01",
                  "2020-10-01","2020-10-01","2020-10-01","2020-10-01","2020-10-01",
                  "2021-01-01","2021-01-01","2021-01-01","2021-01-01","2021-01-01",
                  "2021-01-01","2021-01-01","2021-01-01","2021-01-01","2021-01-01",
                  "2021-01-01","2021-01-01","2021-01-01","2021-01-01"))
GEO <- c(
  "Canada","Newfoundland and Labrador","Prince Edward Island",     
  "Nova Scotia","New Brunswick","Quebec","Ontario","Manitoba","Saskatchewan",             
  "Alberta","British Columbia","Yukon","Northwest Territories","Nunavut",
  "Canada","Newfoundland and Labrador","Prince Edward Island","Nova Scotia",              
  "New Brunswick","Quebec","Ontario","Manitoba","Saskatchewan","Alberta",                  
  "British Columbia","Yukon","Northwest Territories","Nunavut")
JVR <- c(3.5,2.6,3.2,3.3,3.9,4.1,3.4,3.1,2.3,2.4,4.2,4.4,3.0,2.6,
         3.6,2.0,2.5,3.2,3.2,4.2,3.3,3.1,2.7,2.8,4.5,4.7,4.2,3.6)
df <- data.frame(Date=as.Date(Date),GEO=GEO,JVR=JVR)

# 修正后绘图代码
ggplot(filter(df,Date>=as.Date("2020-10-01")),
       aes(x=as.factor(Date),y=JVR,fill=GEO)) +
  geom_bar(stat="identity",position=position_dodge(width=0.9)) +
  geom_text(aes(label=JVR),position=position_dodge(width=0.9),
            vjust=-0.3,size=3) +
  labs(x="季度")

如果需要保留x轴为日期格式，不需要转因子，只需要把geom_text的position_dodge(width=0.9)调整为position_dodge(width=20)即可对齐。

内容的提问来源于stack exchange，提问作者Phil Smith