ansaurus

Question

Answer 1

+5 A:

Both the match() (returns the first appearance) and %in% (returns a Boolean) functions are designed for this.

v <- c('a','b','c','e')

'b' %in% v
## returns TRUE

match('b',v)
## returns 1

dataspora 2009-07-23 02:25:24

Why do you ask a question and then answer it yourself 3 minutes later? What's the point?...

Alex 2009-07-23 02:30:21

Have you heard of FlashMob??? http://blog.stackoverflow.com/2009/07/stack-overflow-flash-mobs/

jjnguy 2009-07-23 02:33:23

match('b',v) should return the index of the first element in v that matches the string 'b'. In this case it would be 2.

Sharpie 2009-07-23 02:34:13

wow, this is an awesome flash mob... i've seen three questions in the past half hour tagged <r>

geowa4 2009-07-23 02:44:32

Good idea, folks! (@jjnguy: no, I hadn't heard of it!!! :-))

ars 2009-07-23 03:13:18

using `%in%` makes the test extendible to set inclusion: `all(candidates %in% container)`.

mariotomo 2010-06-16 11:31:11

Answer 2

+3 A:

You can use the %in% operator:

vec <- c(1, 2, 3, 4, 5)
1 %in% vec # true
10 %in% vec # false

ars 2009-07-23 02:25:52

Answer 3

+2 A:

The any() function makes for readable code

> w <- c(1,2,3)
> any(w==1)
[1] TRUE

> v <- c('a','b','c')
> any(v=='b')
[1] TRUE

> any(v=='f')
[1] FALSE

Dan Goldstein 2009-08-20 22:12:04

R function for testing if a vector contains a given element