Check for a list of strings (words) in a text (phrase)

Question

Is there an elegant way, other than looping, to test if a word which belong to a list is found in a phrase? I'm thinking something like list comprehension of one of the `apply` functions. Ex: ``` words <- c("word1", "word2", "word3") text <- "This is a text made off of word1 and possibly word2 and so on." ``` The output should return TRUE if any of the words is founded in text and which word is founded.

Accepted Answer

`grepl` to the rescue.

```
sapply(words, grepl, text)

# word1 word2 word3 
#  TRUE  TRUE FALSE
```

This considers each element of `words`, in turn, and returns a logical (`TRUE` if the the word appears in `text`, and `FALSE` if not).

If you want to ensure that the exact words are sought, then you can use:

```
sapply(words, function(x) grepl(sprintf('\b%s\b', x), text))
```

This will prevent `word1` from returning `TRUE` when text has `sword123` but lacks `word1`. It might make less sense though if `words` has multi-word elements.

Check for a list of strings (words) in a text (phrase)

Solution

Problem