使用ggplot2手动调整条形图宽度：width参数无效求助

尝试通过geom_bar的width参数调整条形图的条形宽度，但该参数并未生效，需要将条形设置得更窄。以下是使用的代码：

library(ggplot2)
library(tidyverse)
color_table <- tibble(
  Land_cover = c("A", "B", "C", "D"),
  Color = c("yellow", "darkgreen", "blue4", "maroon3")
)

df <- data.frame(
  name=c("FM_BICEP","FM_NR","FM_TRICEP","FM_H_GRASP1","FM_CS_SPE","FM_MOS_SFL","FM_H_GRASP3*","FM_FS_RET","FM_W_SE3","FM_FS_ABD*","FM_MOS_SAB") ,  
  value=c(1.7,1.8,1.8,22.0,26.8,27.4,27.9,31.8,33.4,35.8,35.8),
  group=c("A","A","A","C","D","A","C","A","B","A","A")
)

df$name <- factor(df$name, levels = df$name)
df$group <- factor(df$group, levels = color_table$Land_cover)

# Barplot
ggplot(df, aes(x=name, y=value,fill = group)) +
  geom_bar(stat = "identity", aes(fill=group))+
  theme(axis.text.x = element_text(angle = 90, vjust = 0.5, hjust=1))+
   scale_fill_manual(values = color_table$Color) + geom_col(width = 0.4)

原因分析 #

代码中同时调用了geom_bar(stat = "identity")和geom_col()，这两个函数功能完全重复——geom_col()本质就是geom_bar(stat = "identity")的简写。这导致你设置的width参数只作用在geom_col上，但geom_bar已经先绘制了一层默认宽度的条形，覆盖了geom_col的效果，所以看起来width参数没生效。

解决方案 #

删除其中一个重复的geom函数，将width参数放到保留的函数中即可：

方案1：保留geom_bar并设置width #

library(ggplot2)
library(tidyverse)
color_table <- tibble(
  Land_cover = c("A", "B", "C", "D"),
  Color = c("yellow", "darkgreen", "blue4", "maroon3")
)

df <- data.frame(
  name=c("FM_BICEP","FM_NR","FM_TRICEP","FM_H_GRASP1","FM_CS_SPE","FM_MOS_SFL","FM_H_GRASP3*","FM_FS_RET","FM_W_SE3","FM_FS_ABD*","FM_MOS_SAB") ,  
  value=c(1.7,1.8,1.8,22.0,26.8,27.4,27.9,31.8,33.4,35.8,35.8),
  group=c("A","A","A","C","D","A","C","A","B","A","A")
)

df$name <- factor(df$name, levels = df$name)
df$group <- factor(df$group, levels = color_table$Land_cover)

# Barplot
ggplot(df, aes(x=name, y=value,fill = group)) +
  geom_bar(stat = "identity", width = 0.4)+
  theme(axis.text.x = element_text(angle = 90, vjust = 0.5, hjust=1))+
  scale_fill_manual(values = color_table$Color)

方案2：保留geom_col并设置width #

library(ggplot2)
library(tidyverse)
color_table <- tibble(
  Land_cover = c("A", "B", "C", "D"),
  Color = c("yellow", "darkgreen", "blue4", "maroon3")
)

df <- data.frame(
  name=c("FM_BICEP","FM_NR","FM_TRICEP","FM_H_GRASP1","FM_CS_SPE","FM_MOS_SFL","FM_H_GRASP3*","FM_FS_RET","FM_W_SE3","FM_FS_ABD*","FM_MOS_SAB") ,  
  value=c(1.7,1.8,1.8,22.0,26.8,27.4,27.9,31.8,33.4,35.8,35.8),
  group=c("A","A","A","C","D","A","C","A","B","A","A")
)

df$name <- factor(df$name, levels = df$name)
df$group <- factor(df$group, levels = color_table$Land_cover)

# Barplot
ggplot(df, aes(x=name, y=value,fill = group)) +
  geom_col(width = 0.4)+
  theme(axis.text.x = element_text(angle = 90, vjust = 0.5, hjust=1))+
  scale_fill_manual(values = color_table$Color)

内容的提问来源于stack exchange，提问作者Ana