如何将两个geom_col绘图的对应条形并排合并？

要让两个geom_col的对应条形并排，核心是给两个图层的x轴位置设置偏移量，避免重叠。结合你已用的ggnewscale实现双填充刻度，具体代码如下：

library(ggplot2)
library(ggnewscale)

df<-data.frame(names=c("A","B","C","D","E","F","G","H","I"), 
               frequency=c(0.1,0.7,0.2,0.4,0.4,0.2,0.8,0.1,0.1),
               group=c("1","2","3","3","2","1","1","2","3"))

ggplot(df) +
  # 第一组条形：按group填充，x轴向左偏移0.2
  geom_col(aes(x = as.numeric(group) - 0.2, y = frequency, fill = group), 
           width = 0.4) +
  scale_fill_manual(values=c("#CCCCCC","#ABABAB","#818181"), name = "Group") +
  # 切换填充刻度
  new_scale_fill() +
  # 第二组条形：按names填充，x轴向右偏移0.2
  geom_col(aes(x = as.numeric(group) + 0.2, y = frequency, fill = names), 
           width = 0.4) +
  # 还原x轴刻度为原group字符，保证可读性
  scale_x_continuous(breaks = 1:3, labels = c("1","2","3"), name = "group")

关键细节说明： #

• 将group转为数值型后，通过±0.2给两组条形设置左右偏移，实现并排效果。
• 设置width=0.4，保证两组条形总宽度（0.4+0.4=0.8）不会超出x轴刻度间距，避免拥挤。
• 用scale_x_continuous将数值化的x轴刻度还原为原始group字符，保持图表展示逻辑一致。

内容的提问来源于stack exchange，提问作者Kübra Çelikbaş