R grep: Match one string against multiple patterns

Question

In R, grep usually matches a vector of multiple strings against one regexp.

Q: Is there a possibility to match a single string against multiple regexps? (wi

Answer 1

To expand on the other answer, to transform the sapply() output into a useful logical vector you need to further use an apply() step.

keywords <- c("dog", "cat", "bird")
strings <- c("Do you have a dog?", "My cat ate by bird.", "Let's get icecream!")
(matches <- sapply(keywords, grepl, strings, ignore.case=TRUE))
#        dog   cat  bird
# [1,]  TRUE FALSE FALSE
# [2,] FALSE  TRUE  TRUE
# [3,] FALSE FALSE FALSE

To know which strings contain any of the keywords (patterns):

apply(matches, 1, any)
# [1]  TRUE  TRUE FALSE

To know which keywords (patterns) were matched in the supplied strings:

apply(matches, 2, any)
#  dog  cat bird 
# TRUE TRUE TRUE