[R] Detecting duplicate values

[Charles C. Berry]

On Thu, 14 Aug 2008, Steven McKinney wrote:

>
>> -----Original Message-----
>> From: r-help-bounces at r-project.org
> [mailto:r-help-bounces at r-project.org]
>> On Behalf Of rkevinburton at charter.net
>> Sent: Thursday, August 14, 2008 2:00 PM
>> To: r-help at r-project.org
>> Subject: [R] Detecting duplicate values
>>
>> This is another "how do I do it" type of question. It seems that for a
>> function that I have it has a hard time with lists that have a single
>> repeated value. I want a function (or expression)  that will detect
> this
>> condition. I want to detect:
>>
>> c(2,2,2,2,2)
>> OR
>> c(1)
>>
>> The following is OK
>>
>> c(2,3,3,2)
>> OR
>> c(1,2,1)
>>
>> These lists are "OK" because they have another value in the list. In
> other
>> words I want to detect if there is only one element in the list that
>> repeats 1 or more times.
>>
>> Will length(table(a)) = 1 always work? If so I have answered my own
>> question. If not please bear with me as I have missed a case.
>
> Consider also
> length(unique(a)) == 1

Caveat:

  length(unique( c(1, NA )))
[1] 2
>

which may not be what Kevin wants.

Alternatives:

 	length( na.omit( unique( c(1, NA ) )) ) == 1

 	!isTRUE( any( a[1] != a[-1] )

HTH,

Chuck


>
> Steve McKinney
>
>>
>> Thank you.
>>
>> Kevin
>>
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>> PLEASE do read the posting guide http://www.R-project.org/posting-
>> guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

Charles C. Berry                            (858) 534-2098
                                             Dept of Family/Preventive Medicine
E mailto:cberry at tajo.ucsd.edu	            UC San Diego
http://famprevmed.ucsd.edu/faculty/cberry/  La Jolla, San Diego 92093-0901