R语言 使用ggplot2绘制boxplot

1、输入数据

heartrt <- data.frame(hr=c(56,53,53,65,70,58,51,
                           78,62,70,73,67,75,65,
                           77,86,65,83,79,80,77),
                      class=gl(3,7,labels = c("Nonsmoker","Lightsmoker","Heavysmoker"))) #gl()生成因子heartrt <- data.frame(hr=c(56,53,53,65