删除子文本数组之前的文本

Question

我有一组需要操作的字符串。对于每个字符串，如果它们包含一组子字符串，我想保留该子字符串，否则保持不变。

下面是一个示例:

keep <- c("USA","UNITED STATES")
keep <- paste0(paste0(" ",keep,"$"),collapse="|")

data <- c("DETROIT","DETROIT USA","DETROIT UNITED STATES")
expected_result <- c("DETROIT","USA","UNITED STATES")

Answer 1

你可以使用

data <- c("DETROIT","DETROIT USA","DETROIT UNITED STATES")
keep <- c("USA","UNITED STATES")

regex <- paste0(".*\\s*\\b(",paste0(keep,collapse="|"), ")\\b")
sub(regex, "\\1", data)
## => [1] "DETROIT"       "USA"           "UNITED STATES"

请参阅R demo online .

正则表达式为.*\s*\b(USA|UNITED STATES)\b，参见its online demo .

详细信息:

• .* - 任意零个或多个尽可能多的字符
• \s* - 零个或多个空格
• \b(USA|UNITED STATES)\b - 整个单词 USA 或 UNITED STATES，捕获到第 1 组 (\1 在替换模式中)。