如何用ggplot绘制右侧分组加宽的组合箱线图？

要实现右侧（Photochemistry）箱线图比左侧（Gas exchange）更宽的效果，核心是给两个区域的箱线图绑定不同宽度参数，具体步骤如下：

1. 给数据添加区域标识列 #

先区分左右区域的x轴变量，给dff和df1添加区域标记列（假设前7个x变量属于Gas exchange区域，可根据实际变量位置调整判断条件）：

# 给主数据框和文本数据框添加区域标识
dff$region <- ifelse(as.integer(dff$variable) <= 7, "gas", "photo")
df1$region <- ifelse(as.integer(df1$variable) <= 7, "gas", "photo")

2. 修改ggplot代码，绑定宽度到区域 #

调整原代码中箱线图和误差线的宽度映射，同时修正文本的偏移对齐：

ggplot(dff, aes(x=variable, y=value, fill=Specie, width=region)) +
  stat_boxplot(geom = "errorbar", col="red")+
  scale_fill_manual(values=c('#FFC7CE','#FFEB9C','#C6EFCF'))+
  # 自定义左右区域箱线图宽度：左侧窄，右侧宽
  scale_width_manual(values = c(gas = 0.6, photo = 0.8))+
  geom_boxplot(outlier.shape = NA,linetype = 1)+ 
  theme_bw()+
  geom_text(data = df1, aes(y = up+0.02, label = label), fontface="italic", 
            size=2.5, position = position_dodge(width = aes(width=region)), 
            hjust=0.4, col="blue")+
  theme(axis.text.x = element_text(size = 10, colour = "black", family = "serif"),
        axis.text.y = element_text(size = 10, colour = "black"),
        panel.grid.minor = element_blank(),
        legend.position = c(0.5, 1.05), legend.background = element_blank(),
        legend.direction = "horizontal", legend.title = element_blank(),
        legend.text = element_text(size = 9, face="italic", colour = "black")) + 
  scale_x_discrete(labels=c(l1,l2,l3,l4,l5,l6,l7,l8,l9,l10,l11,l12)) + 
  scale_y_continuous(breaks = seq(0, 1, 0.1),sec.axis = sec_axis(~.*1, breaks = seq(0, 1, 0.1))) + 
  labs(title = "",subtitle = "",y = y, x = "")+ 
  geom_vline(xintercept= 7.5, colour="black",linetype="dashed")+
  geom_vline(xintercept= 12.5, colour="black",linetype="solid")+
  annotate(geom="text", x=1.1, y=1.02, label="Gas exchange",family="serif",
           fontface="bold",size=3.5)+
  annotate(geom="text", x=8.2, y=1.02, label="Photochemistry",family="serif",
           fontface="bold",size=3.5)

关键修改说明 #

• 在全局aes中加入width=region，让箱线图宽度与区域绑定；
• 用scale_width_manual自定义宽度数值，gas对应左侧区域，photo对应右侧区域，数值越大箱线图越宽（可根据需求调整0.6/0.8这类数值）；
• 调整geom_text的position_dodge参数为aes(width=region)，确保标注文本与对应区域的箱线图对齐。

内容的提问来源于stack exchange，提问作者Ikram Bashir