R语言中 ggplot函数中 annotate选项

library(ggplot2)
p <- ggplot(faithful, aes(x = eruptions, y = waiting)) + 
  geom_point()                  ## 基础绘图
p

p + annotate("text", x = 3, y = 48, label = "Group 1") + 
annotate("text", x = 4.5, y = 66, label = "Group 2")          ## 增加文本

p + annotate("text", x = 3, y = 48, label = "Group 1", 
    family = "serif", fontface = "italic", colour = "darkred",
    size = 5) + annotate("text", x = 4.5, y = 66, 
    label = "Group 2", family = "serif", fontface = "italic", 
    colour = "darkred", size = 5)            ## 设置颜色、字体、大小等

p + annotate("text",x=3,y=48,label="Group 1", alpha=.1) +
  geom_text(x=4.5, y=66, label="Group 2", alpha=.1)          ## 等价geom_text

p + annotate("text", x = -Inf, y = Inf, label = "Upper left", 
             hjust = -0.2,vjust = 2) + 
annotate("text", x = mean(range(faithful$eruptions)), y = -Inf, 
                      vjust = -0.4, label = "Bottom middle")       ## 指定位置02