如何手动将图例添加到ggplot和geom_point？

# 安装并加载ggplot2包
if (!requireNamespace("ggplot2", quietly = TRUE)) {
  install.packages("ggplot2")
}
library(ggplot2)

# 创建数据集
data <- data.frame(
  x = rnorm(100),
  y = rnorm(100),
  group = sample(c("A", "B"), 100, replace = TRUE)
)

# 创建ggplot对象并添加geom_point
p <- ggplot(data, aes(x = x, y = y, color = group)) +
  geom_point(size = 3)

# 手动调整图例
p + theme(legend.position = "bottom", legend.title = element_text("Group"))

# 更多自定义选项
p + guides(color = guide_legend(title.position = "top", nrow = 2)) +
  theme(legend.position = c(0.8, 0.2), legend.background = element_rect(fill = "white"))

# 确保在aes()中指定了color
ggplot(data, aes(x = x, y = y, color = group)) +
  geom_point() +
  theme(legend.position = "bottom")