R grep: is there an AND operator?
Thanks to this answer, this regex seems to work. You want to use grepl()
which returns a logical to index into your data object. I won't claim to fully understand the inner workings of the regex, but regardless:
x <- c("imageUploaded,people.jpg,more,comma,separated,stuff", "imageUploaded", "people.jpg")
grepl("(?=.*imageUploaded)(?=.*people\\.jpg)", x, perl = TRUE)
#-----
[1] TRUE FALSE FALSE
I love @Chase's answer, and it makes good sense to me, but it can be a bit dangerous to use constructs that one doesn't totally understand.
This answer is meant to reassure anyone who'd like to use @thelatemail's more straightforward approach that it works just as well and is completely competitive speedwise. It's certainly what I'd use in this case. (It's also reassuring that the more sophisticated Perl-compatible-regex pays no performance cost for its power and easy extensibility.)
library(rbenchmark)
x <- paste0(sample(letters, 1e6, replace=T), ## A longer vector of
sample(letters, 1e6, replace=T)) ## possible matches
## Both methods give identical results
tlm <- grepl("a", x, fixed=TRUE) & grepl("b", x, fixed=TRUE)
pat <- "(?=.*a)(?=.*b)"
Chase <- grepl(pat, x, perl=TRUE)
identical(tlm, Chase)
# [1] TRUE
## Both methods are similarly fast
benchmark(
tlm = grepl("a", x, fixed=TRUE) & grepl("b", x, fixed=TRUE),
Chase = grepl(pat, x, perl=TRUE))
# test replications elapsed relative user.self sys.self
# 2 Chase 100 9.89 1.105 9.80 0.10
# 1 thelatemail 100 8.95 1.000 8.47 0.48
For readability's sake, you could just do:
x <- c(
"imageUploaded,people.jpg,more,comma,separated,stuff",
"imageUploaded",
"people.jpg"
)
xmatches <- intersect(
grep("imageUploaded",x,fixed=TRUE),
grep("people.jpg",x,fixed=TRUE)
)
x[xmatches]
[1] "imageUploaded,people.jpg,more,comma,separated,stuff"