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

From: Marc Schwartz <marc_schwartz_at_comcast.net>
Date: Sat 20 Jan 2007 - 18:58:04 GMT

On Sat, 2007-01-20 at 13:30 -0500, lindeman@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



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