如何使用R ggplot绘制对照组与处理组并列的分组柱状图

修改方案 #

你当前代码输出分面图的原因是调用了facet_wrap(~treatment)语句，要实现同分类下对照组/处理组柱子并列，只需做两处调整：

• 删除facet_wrap分面代码
• 在aes()映射中添加fill = treatment，将处理分组映射为柱子填充色，让position = "dodge"参数识别需要并列的分组

完整可运行代码 #

library(ggplot2)
library(tibble)

# 示例数据
example <- tribble(
  ~treatment, ~categorical_var, ~n,
  "control",            "1",    10,
  "control",            "2",    12,
  "control",            "3",     7,
  "treatment",          "1",     14,
  "treatment",          "2",     5,
  "treatment",          "3",     11,
)

# 绘图代码
ggplot(example, aes(x = categorical_var, y = n, fill = treatment)) + 
  geom_col(position = "dodge")

注：geom_col()等价于geom_bar(stat = "identity")，是汇总值柱状图的更简洁写法。如果要保留原写法也可以替换为：

ggplot(example, aes(categorical_var, n, fill = treatment)) + 
  geom_bar(position="dodge",stat="identity")

可选美化 #

可以添加标签层自定义轴标题和图例名称：

ggplot(example, aes(x = categorical_var, y = n, fill = treatment)) + 
  geom_col(position = "dodge") +
  labs(x = "分类变量", y = "计数", fill = "实验分组")

内容的提问来源于stack exchange，提问作者Quinoba