单元格合并
单元格的合并使用 unite()，选项参数逻辑为：
- 指定待合并列 A
- 指定待合并列 B
- 指定合并的新列名
table5 |> unite(century, year, col = "year", sep = "")单元格拆分
table3 |> separate_wider_delim(col = rate, delim = "/", names = c("cases", "pop"))单元格的合并使用 unite()，选项参数逻辑为：
table5 |> unite(century, year, col = "year", sep = "")table3 |> separate_wider_delim(col = rate, delim = "/", names = c("cases", "pop"))