# [R] match and incomparables

Bert Gunter gunter.berton at gene.com
Sat Sep 13 00:43:37 CEST 2008

```Looks like a bug to me. Compare:

> match (1:3,1:3,incom=3)
[1] 1 2 3
> match (1:3,1:3,incom=2:3)
[1] 1 2 3
> match (1:3,1:3,incom=1:2)
[1] NA NA  3
> match (1:3,1:3,incom=1)
[1] NA  2  3

Cheers,
Bert

-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On
Behalf Of Adam D. I. Kramer
Sent: Friday, September 12, 2008 3:06 PM
To: McGehee, Robert
Cc: r-help
Subject: Re: [R] match and incomparables

I can replicate this and also do not understand it.

> match(1:3,1:3,incomparables=5)
[1] NA  2  3
> match(1:3,1:3,incomparables=4)
[1] 1 2 3
> match(1:3,1:3,incomparables=3)
[1] 1 2 3
> match(1:3,1:3,incomparables=2)
[1] 1 2 3
> match(1:3,1:3,incomparables=1)
[1] NA  2  3

...every other integer value for incomparables produces 1 2 and 3 for
output. I'm using R 2.7.2, self-compiled, under linux.

On Fri, 12 Sep 2008, McGehee, Robert wrote:

> Hello,
> I was playing around with the newly implemented 'incomparables' argument
> in 'match' and realized the argument does not behave anything like I
> expected. Can someone explain what is going on here? Sorry if I'm
>
>> match(1:3, 1:3, incomparables=1)
> [1] NA  2  3  # This seems right, the 1 in 'x' is 'incomparable'
>
>> match(1:3, 1:3, incomparables=2)
> [1] 1  2  3   # Shouldn't this be 1 NA 3? Why isn't the 2 incomparable?
>
>> match(1:3, 1:3, incomparables=5)
> [1] NA  2  3   # Why isn't the 5 ignored?
>
> Note from ?match:
> "incomparables: a vector of values that cannot be matched. Any value in
> x matching a value in this vector is assigned the nomatch value. For
> historical reasons, FALSE is equivalent to NULL."
>
> Robert
>
> platform       i386-pc-mingw32
> arch           i386
> os             mingw32
> system         i386, mingw32
> status
> major          2
> minor          7.2
> year           2008
> month          08
> day            25
> svn rev        46428
> language       R
> version.string R version 2.7.2 (2008-08-25)
>
> Robert McGehee, CFA
> Geode Capital Management, LLC
> One Post Office Square, 28th Floor | Boston, MA | 02109
> Tel: 617/392-8396    Fax:617/476-6389
> mailto:robert.mcgehee at geodecapital.com
>
>
>
> This e-mail, and any attachments hereto, are intended fo...{{dropped:12}}
>
> ______________________________________________
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> and provide commented, minimal, self-contained, reproducible code.
>

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