按老师输入的输入后出来的结果不一样，有错误

> y <- 1:4

> y

[1] 1 2 3 4

> names(y) <- c("a" "b" "c" "d")

错误: unexpected string constant in "names(y) <- c("a" "b""

> y

[1] 1 2 3 4

> y[2]

[1] 2

> names(y) <- ("a","b","c","d")

错误: 意外的',' in "names(y) <- ("a","

> y

[1] 1 2 3 4