1 回答sapply(s,function(x) colMeans(x[,c("Ozone","Wind","Temp")]為什么寫成sapply(s, colMeans(s[,c("Ozone","Wind","Temp")]就不行呢

4 回答Error in `[.data.frame`(z, , c("Ozone", "wind", "Temp")) : 選擇了未定義的列

2 回答為什么不可以直接寫成sapply(s, colMeans(x[,c("Ozone","Wind","Temp")]

1 回答按老師輸入的輸入后出來的結果不一樣，有錯誤

1 回答輸入函數錯誤