Remove Leading/Trailing Whitespace
作用：去掉字符串头/尾的空格。

1. Description

Remove leading and/or trailing whitespace from character strings.

2. Usage

trimws(x, which = c("both", "left", "right"))

3. Arguments

x
a character vector
which
a character string specifying whether to remove both leading and trailing whitespace (default), or only leading ("left") or trailing ("right"). Can be abbreviated.
Details

For portability, ‘whitespace’ is taken as the character class [ \t\r\n] (space, horizontal tab, line feed, carriage return).

4. Examples

    x <- "  Some text. "
    x
    trimws(x)
    trimws(x, "l")
    trimws(x, "r")