[R] issues with identical()

[Prof Brian Ripley]

On Fri, 20 May 2005, Jean Eid wrote:

> Hi all, hope you having a nice day,
>
> I ahve this weird results with identical (probably I am not understanding
> correctly what it does ...)

Why should

     a data frame with colunns pub_id faminc90
     a data frame with colunns pub_id faminc

be considered identical()?  Its description is

      The safe and reliable way to test two objects for being _exactly_
      equal.

and those are not equal in a critical way.

> I have these two data frames and I issue :
>> identical(temp, temp1)
> [1] FALSE
>
>
> However, these data frames are Nx2 and when I issue:
>> identical(temp[,2], temp1[,2])
> [1] TRUE
>> identical(temp[,1], temp1[,1])
> [1] TRUE
>
> and the results from str
>
>
>> str(temp)
> `data.frame':	7072 obs. of  2 variables:
> $ pub_id  : int  10000 1000 10001 10002 10003 10004 10005 10006 10007
> $ faminc90: int  -2 5998 19900 43000 35000 40000 56538 61000 36000 39105
>> str(temp1)
> `data.frame':	7072 obs. of  2 variables:
> $ pub_id: int  10000 1000 10001 10002 10003 10004 10005 10006 10007 10008
> $ faminc: int  -2 5998 19900 43000 35000 40000 56538 61000 36000 39105
>
> The question is why are the objects different. How else can I tell what is
> the difference

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595