# [R] Bug in "is" ?

ctu at bigred.unl.edu ctu at bigred.unl.edu
Wed Sep 24 07:05:03 CEST 2008

```This is really bothering me! In the Dr. Venables and Dr. Ripley's book
"S Programming" Page 105
shows that
> c(is(10,"integer"),is(10.5,"integer"))
[1] T F

But I try this in R 2.7.2 it shows
> c(is(10,"integer"),is(10.5,"integer"))
[1] FALSE FALSE
Does anyone know what is going on here?

Appreciate,
Chunhao

Quoting Yihui Xie <xieyihui at gmail.com>:

> Yes, everyone will agree "7" is an integer, but I don't think
> computers will agree too :-) R thinks it's a double-precision number,
> except when you explicitly specify it as an integer (say,
> as.integer()).
>
>> class(7)
> [1] "numeric"
>
>> is.double(7)
> [1] TRUE
>
> Regards,
> Yihui
> --
> Yihui Xie <xieyihui at gmail.com>
> Phone: +86-(0)10-82509086 Fax: +86-(0)10-82509086
> Mobile: +86-15810805877
> Homepage: http://www.yihui.name
> School of Statistics, Room 1037, Mingde Main Building,
> Renmin University of China, Beijing, 100872, China
>
>
>
> On Wed, Sep 24, 2008 at 12:40 PM,  <ctu at bigred.unl.edu> wrote:
>> Hi R users
>> Is there anything wrong in "is" function? (R 2.7.2)
>> I believe that everyone will agree that "7" is an integer, right? but why R
>> shows 7 is not an integer
>>
>>> is.integer(7)
>>
>> [1] FALSE
>>>
>>> is(7,"integer")
>>
>> [1] FALSE
>>>
>>> is(as.integer(7), "integer")
>>
>> [1] TRUE
>>
>> Thank you very much in advance
>> Chunhao
>>
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