[R] data encapsulation with classes

[Roger Bivand]

On Sun, 8 Apr 2007, Peter Williams wrote:

> Hi All,
> 
> I'm new to R from a C and Octave/Matlab background.  I am trying to  
> construct some classes in R to which I want to attach pieces of data.
> First, is attr(obj, 'member name') <- data the accepted way of doing  
> this?

No, it isn't. You seem to be trying to deduce new-style classes from a
representation used before R 2.4, but in any case it would not be
sensible. Please consult John M. Chambers. Programming with Data.
Springer, New York, 1998, and/or William N. Venables and Brian D. Ripley.
S Programming. Springer, New York, 2000, or for a shorter online resource:

http://www.stat.auckland.ac.nz/S-Workshop/Gentleman/Methods.pdf

> 
> Second, having attached member data with attr is there anything wrong  
> with accessing it by the asperand (@), i.e.
> 
>  > t = ""
>  > attr(t, 'test') <- 4
>  > t at test
> [1] 4
> 
> I can't find any documentation on using the asperand to access  
> attributes like this.  I saw it in a piece of code as I was googling  
> around trying to find some information on attaching data to a class  
> in R.  Is this deprecated?  Is this poor form?  If anyone has some  
> suggestions please let me know.
> 
> Thank you
> 
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> and provide commented, minimal, self-contained, reproducible code.
> 

-- 
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: Roger.Bivand at nhh.no