[R] simple q: returning a logical vector of substring matches

[Marc Schwartz]

On Sat, 2007-01-20 at 13:30 -0500, lindeman at bard.edu wrote:
> I'm a relative R novice, and sometimes the simple things trip me up.
> 
> Suppose I have
> 
> a <- c("apple", "pear")
> 
> and I want a logical vector of whether each of these strings contains  
> "ear" (in this case, F T). What is the idiom?
> 
> Quizzically,
> Mark Lindeman

See ?grep and ?regexp

a <- c("apple", "pear")

> grep("ear", a)
[1] 2

> grep("ear", a, value = TRUE)
[1] "pear"

If you actually want the answer to be FALSE TRUE, then:

> a %in% grep("ear", a, value = TRUE)
[1] FALSE  TRUE

In that case see ?"%in%"

HTH,

Marc Schwartz