Error in `[.data.frame`(z, , c("Ozone", "wind", "Temp")) : 选择了未定义的列

源自：4-5 R语言函数 split

head(airquality)

s <- split(airquality,airquality$Month)

table(airquality$Month)
lapply(s,function(z) colMeans(z[,c("Ozone","wind","Temp")]))
sapply(s,function(z) colMeans(z[,c("Ozone","wind","Temp")]))

win 10, 3,3,2版本，运行出错

Error in `[.data.frame`(z, , c("Ozone", "wind", "Temp")) : 选择了未定义的列

提问者：李_sir 2017-05-03 14:25