Replace punctuation in string

Question

I want to replace the punctuation in a string by adding '\\' before the punctuation. The reason is I will be using regex on the string afterwards and it fails if there is a question mark without '\\' in front of it.

So basically, I would like to do something like this:

gsub("\\?","\\\\?", x)

Which converts a string "How are you?" to "How are you\\?" But I would like to do this for all punctuation. Is this possible?

I don't have experience with r, but `gsub("\\([.?])","\\\\$1",x)` or `gsub("\\([.?])","\\\\\\1",x)` should work. — Aran-Fey, Feb 23 '17 at 16:56
Depending on your use case, you may be able to skip this step and just use the `fixed = TRUE` argument in your subsequent regex. — Gregor Thomas, Feb 23 '17 at 16:59
I think probably you have it backwards. The target string never has to be escaped. Only the regex string string with literal metachar's (ie. `?*+`, etc) need to be escaped. — , Feb 23 '17 at 17:10
What are you trying to do? I don't think answering this question will help you get your real task done properly — MichaelChirico, Feb 23 '17 at 17:13
[More good reading here](http://stackoverflow.com/a/27721009/903061). In addition to `fixed`, another easy solution would be to use `\\Q` and `\\E` at the start and end of your strings. — Gregor Thomas, Feb 23 '17 at 17:21

score 3 · Accepted Answer · answered Feb 23 '17 at 17:08

You can use gsub with the [[:punct:]] regular expression alias as follows:

> x <- "Hi! How are you today?"
> gsub('([[:punct:]])', '\\\\\\1', x)
[1] "Hi\\! How are you today\\?"

Note the replacement starts with '\\\\' to produce the double backslash you requested while the '\\1' portion preserves the punctuation mark.

Replace punctuation in string

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