在 R 中搜索以 X 开头的整个单词

Question

I need to blank-out certain words in various phrases, but because the words may be conjugated, plural, or possessive, I can only look for the first few letters. An example:

example = "You are the elephant's friend."
gsub("\\beleph.*\\b", " _____ " , example)
[1] "You are the  _____ "

How can I match the entire word from the first few letters?

Answer 1

gsub("\\beleph[[:alpha:][:punct:]]+\\b", "_____" , example)
[1] "You are the _____ friend."

works in this instance.

The change is replacing the greedy (and sometimes dangerous) ".*" matching anything and everything regex with the character class "[[:alpha:][:punct:]]+", which matches alphabetical characters and punctuation characters. See help(regex) for additional ready-made character classes that may be useful, like [:alnum:] in case any strings contain digits as well.

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In order to catch matches with the first word as well, the following should work. Here's an example.

exampleYoda = "elephant's friend you be."

gsub("(\\b|^)eleph[[:alpha:][:punct:]]+\\b", "_____" , exampleYoda)
[1] "_____ friend you be."

which also works with example

gsub("(\\b|^)eleph[[:alpha:][:punct:]]+\\b", "_____" , example)
[1] "You are the _____ friend."

Answer 2

To make your original code work you just have to make the quantifier ungreedy.

example = "You are the elephant's friend."
gsub("\\beleph.*?\\b", " _____ " , example)
[1] "You are the  _____ 's friend."

This solution cause problems with the ' but you can use blank spaces insead, so you can try

example = "You are the elephant's friend."
gsub("\\seleph.*?\\s", " _____ " , example)
[1] "You are the _____ friend."