如何在数字x轴的ggplot中将直接标签添加到条形图

library(ggplot2)

# 创建数据框
data <- data.frame(category = c("A", "B", "C", "D"),
                   value = c(10, 20, 30, 40))

# 创建基本的条形图
p <- ggplot(data, aes(x = category, y = value))

# 添加条形图的图层
p <- p + geom_bar(stat = "identity")

# 添加直接标签
p <- p + geom_text(aes(label = value), vjust = -0.5)

# 调整图表外观
p <- p + labs(x = "Category", y = "Value", title = "Bar Chart with Direct Labels")
p <- p + theme(axis.text.x = element_text(angle = 45, hjust = 1))

# 显示图表
print(p)