在ggplot中更改列/堆栈列的透明度

library(ggplot2)

# 创建一个数据框
data <- data.frame(
  category = c("A", "B", "C"),
  value = c(10, 20, 15)
)

# 创建柱状图，并设置列的透明度为0.5
ggplot(data, aes(x = category, y = value)) +
  geom_col(alpha = 0.5)

library(ggplot2)

# 创建一个数据框
data <- data.frame(
  category = c("A", "B", "C"),
  value1 = c(10, 20, 15),
  value2 = c(5, 10, 8)
)

# 创建堆栈柱状图，并设置堆栈列的透明度为0.5
ggplot(data, aes(x = category)) +
  geom_bar(aes(y = value1, fill = "Value 1"), alpha = 0.5) +
  geom_bar(aes(y = value2, fill = "Value 2"), alpha = 0.5) +
  scale_fill_manual(values = c("Value 1" = "blue", "Value 2" = "red"))