r - R remove string after second underscore

Question

This is a very basic question, but I cannot find a clear answer... How do you remove everything after the second underscore. Thanks!

Please_remove_this_part

desired output:

Please_remove

标签： rstringsubstring

Answer 1

x <- "Please_remove_this_part"
sub("([A-Za-z]+_[A-Za-z]+).*", "\\1", x)
[1] "Please_remove"

此sub解决方案将第二个下划线之前的所有内容定义为捕获组，并通过\\1替换参数中的反向引用来调用它。