# [R] value matching %in% for a number pair

Jim Lemon drjimlemon at gmail.com
Sun Nov 13 06:06:48 CET 2016

```Hi john,
I don't know whether this breaks any rules, but:

target_pair<-c(3,4)
pair_list<-list(c(1,2),c(3,4),c(5,6))
sapply(pair_list,identical,target_pair)
[1] FALSE  TRUE FALSE

Jim

On Sun, Nov 13, 2016 at 1:32 PM, Jeff Newmiller
<jdnewmil at dcn.davis.ca.us> wrote:
> Sorry, that was a fail. Better to think about:
>
> any( 2 == p[,1] & 3 == p[,2] )
> v <- matrix( c( 2,3, 1,2, 5,5 ), byrow=TRUE, ncol=2 )
> apply( v, 1, function(x) { any( x[1]==p[,1] & x[2]==p[,2] ) } )
>
> --
> Sent from my phone. Please excuse my brevity.
>
> On November 12, 2016 6:11:13 PM PST, Jeff Newmiller <jdnewmil at dcn.davis.ca.us> wrote:
>>This really depends on the way you represent these pairs. Here is some
>>food for thought:
>>
>>p <- matrix( c( 1,2, 4,3, 3,3, 2,3, 4,5 ), byrow=TRUE, ncol=2 )
>>( 2 %in% p[,1] ) & ( 3 %in% p[,2] ) # (2,3)
>>( c( 2, 1, 5 ) %in% p[,1] ) & ( c( 3, 2, 5 ) %in% p[,2] ) # (2,3) (1,2)
>>(5,5)
>>
>>--
>>Sent from my phone. Please excuse my brevity.
>>
>>On November 12, 2016 5:36:37 PM PST, John <miaojpm at gmail.com> wrote:
>>>Hi,
>>>
>>>   We can match one numerical value as follows
>>>> 3 %in% c(4,5)
>>>[1] FALSE
>>>> 3 %in% c(4,5,3)
>>>[1] TRUE
>>>
>>>   To see whether value pairs are identical,
>>>> identical(c(3,4), c(3,5))
>>>[1] FALSE
>>>> identical(c(3,4), c(3,4))
>>>[1] TRUE
>>>
>>>   Is there any way to test whether “A value pair is in a set of value
>>>pairs”? For example, can we test whether the pair (2,3) is identical
>>to
>>>one
>>>of the pairs in the set S={(1,2), (4,3), (3,3), (2,3), (4,5)}?
>>> In this case, the answer is yes because the 4th element of S is
>>(2,3).
>>>Is there any simple way to code it? Thanks!
>>>
>>>John
>>>
>>>      [[alternative HTML version deleted]]
>>>
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>>>and provide commented, minimal, self-contained, reproducible code.
>>
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