从数据框中读取列向量用$,即写成Wage$wage.
library(ISLR) library(dplyr) print(class(Wage$wage)) summarise(Wage,count=n(),meanwage=mean(Wage$wage,na.rm=FALSE))
运行结果:
[1] "numeric" count meanwage 1 3000 111.7036
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