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