R getting substrings and regular expressions?
r, regex, string
Solution
Here is a one-liner solution
gsub(".*\\#(.*)\\..*", "\\1", c("HelloWorld#you.txt"))
Output:
you
To explain the code, it matches everything up to `#` and then extracts all word characters up to `.`, so the final output will be the in-between string which what you are looking for.
Edit:
The above solution matches file name up to the last `.` i.e. allow file name to have multiple dots. If you want to extract the name up to the first `.` you can use the regex `.*\\#(\\w*)\\..*` instead.
Problem
I have a set of strings that are file names. I want to extract all characters after the # symbol but before the file extension. For example, one of the file names is: ``` HelloWorld#you.txt ``` I would want to return the string`you` Here is my code: ``` hashPos = grep("#", name, fixed=TRUE) dotPos = length(name)-3 finalText = substring(name, hashPos, dotPos) ``` I read online that `grep` is supposed to return the index where the first parameter occurs (in this case the # symbol). So, I was expecting the above to work but it does not. Or how would I use a regular expression to extract this string? Also, what happens when the string does not have a # symbol? Would the function return a special value such as -1?