R中一个条形图中的多个变量

install.packages("ggplot2")
library(ggplot2)

# 创建一个数据框
data <- data.frame(
  category = c("A", "B", "C", "D"),
  variable1 = c(10, 15, 8, 12),
  variable2 = c(5, 9, 6, 10),
  variable3 = c(7, 11, 9, 13)
)

# 创建条形图
ggplot(data, aes(x = category)) +
  geom_bar(aes(y = variable1, fill = "Variable 1"), stat = "identity", position = "dodge") +
  geom_bar(aes(y = variable2, fill = "Variable 2"), stat = "identity", position = "dodge") +
  geom_bar(aes(y = variable3, fill = "Variable 3"), stat = "identity", position = "dodge") +
  labs(title = "Multiple Variables in a Bar Chart", x = "Category", y = "Value") +
  scale_fill_manual(values = c("Variable 1" = "red", "Variable 2" = "blue", "Variable 3" = "green")) +
  theme_minimal()