使用regexpr函数查找R中的最后一个字符

Question

I am having problem with finding the last character in a string. I am trying to use the regexpr function to check if the last character is equal to / forward slash.

But unfortunately it does work. Can anyone help me? Below is my code.

regexpr( pattern = ".$", text = /home/rexamine/archivist2/ex/// ) != "/"

Answer 1

You can avoid using regular expression and use substr to do this.

> x <- '/home/rexamine/archivist2/ex///'
> substr(x, nchar(x)-1+1, nchar(x)) == '/'
[1] TRUE

Or use str_sub from the stringr package:

> str_sub(x, -1) == '/'
[1] TRUE

Answer 2

^.*\/$

您可以使用它。如果最后一个字符不是/这将失败。

Answer 3

You could use a simple grepl function,

> text = "/home/rexamine/archivist2/ex///"
> grepl("/$", text, perl=TRUE)
[1] TRUE
> text = "/home/rexamine/archivist2/ex"
> grepl("/$", text, perl=TRUE)
[1] FALSE