如何改变堆叠条形图在R中的堆叠位置？

library(ggplot2)

# 创建示例数据
data <- data.frame(
  category = c("A", "B", "C"),
  value1 = c(10, 20, 30),
  value2 = c(15, 25, 35)
)

# 绘制堆叠条形图（默认堆叠位置）
ggplot(data, aes(x = category)) +
  geom_bar(aes(y = value1, fill = "Value 1"), stat = "identity") +
  geom_bar(aes(y = value2, fill = "Value 2"), stat = "identity") +
  labs(fill = "Legend") +
  theme(legend.position = "bottom")

# 绘制填充堆叠条形图
ggplot(data, aes(x = category)) +
  geom_bar(aes(y = value1, fill = "Value 1"), stat = "identity", position = "fill") +
  geom_bar(aes(y = value2, fill = "Value 2"), stat = "identity", position = "fill") +
  labs(fill = "Legend") +
  theme(legend.position = "bottom")

# 绘制分开堆叠条形图
ggplot(data, aes(x = category)) +
  geom_bar(aes(y = value1, fill = "Value 1"), stat = "identity", position = "dodge") +
  geom_bar(aes(y = value2, fill = "Value 2"), stat = "identity", position = "dodge") +
  labs(fill = "Legend") +
  theme(legend.position = "bottom")