issues with identical() - R-help

Jean Eid

Fri, May 20, 2005 9:23 AM #

Hi all, hope you having a nice day,

I ahve this weird results with identical (probably I am not understanding
correctly what it does ...)

I have these two data frames and I issue :

[1] FALSE


However, these data frames are Nx2 and when I issue:

[1] TRUE

[1] TRUE

and the results from str

`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

`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


Thank You

Jean

Duncan Murdoch

Fri, May 20, 2005 9:42 AM #

Jean Eid wrote:

There could be a difference in the attributes (e.g. rownames of the 
dataframe, or names of one of the columns).

One thing that might turn up the difference is to use dump() to write 
out the objects to a file, and use some text-based compare on those files.

Duncan Murdoch

Peter Dalgaard

Fri, May 20, 2005 9:45 AM #

Jean Eid <jeaneid at chass.utoronto.ca> writes:

Just look more carefully. The _names_ differ.

O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)             FAX: (+45) 35327907

Brian Ripley

Fri, May 20, 2005 9:51 AM #

On Fri, 20 May 2005, Jean Eid wrote:

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.

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

Jean Eid

Sat, May 21, 2005 9:22 AM #

Thank you all for pointing out the name of the variables.. I do apologize
for not catching that,..

have a good day,

Jean

On Fri, 20 May 2005, Prof Brian Ripley wrote: