How to grep a vector and return a single TRUE or FALSE?

Question

Is there a grep function in R that returns TRUE if a pattern is found anywhere in the given character vector and FALSE otherwise?

Answer 1

possibly a combination of grepl() and any()?

like

> foo = c("hello", "world", "youve", "got", "mail")
> any(grepl("world", foo))
[1] TRUE
> any(grepl("hi", foo))
[1] FALSE  
> any(grepl("hel", foo))
[1] TRUE

your questions a little unclear as to whether you want that last example to return true or not

Answer 2

grepl is what you are looking for

grepl("is", "This is grepl test")
[1] TRUE
grepl("is not", "This is grepl test")
[1] FALSE

Answer 3

Are you looking for "any"?

> x<-c(1,2,3,4,5)
> x==5
[1] FALSE FALSE FALSE FALSE  TRUE
> any(x==5)
[1] TRUE

Note that you can do this for strings as well

> x<-c("a","b","c","d")
> any(x=="b")
[1] TRUE
> any(x=="e")
[1] FALSE

And it can be convenient when combined with applies:

> sapply(c(2,4,6,8,10), function(x){ x%%2==0 }  )
[1] TRUE TRUE TRUE TRUE TRUE
> any(sapply(c(2,4,6,8,10), function(x){ x%%2!=0 }  ))
[1] FALSE

Answer 4

Perhaps you're looking for grepl()?

> grepl("is", c("This", "is", "a", "test", "isn't", "it?"))
[1]  TRUE  TRUE FALSE FALSE  TRUE FALSE

Where the first argument is the pattern you're looking for, the second argument is the vector against which you want to match, and the returned value is a Boolean vector of the same length describing whether or not the pattern was matched to each element.