Hi Charlie,

Thank you! I will certainly follow your advice.

Cheers!!

Albert-Jan



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

In the face of ambiguity, refuse the temptation to guess.

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--- On Thu, 3/25/10, Sharpie <chuck@sharpsteen.net> wrote:

From: Sharpie <chuck@sharpsteen.net>
Subject: Re: [R] Abstract classes
To: r-help@r-project.org
Date: Thursday, March 25, 2010, 5:02 PM



Albert-Jan Roskam wrote:
> 
> Hi R lovers,
> 
> I'm looking for more information about, and implementations of abstract
> classes. After reading "Head First Design Patterns" (O'Reilly). I want to
> know whether I could use this to build an interface, i.e. a placeholder
> for all possible methods in the underlying subclasses. The final goal is
> to end up with a more flexible/extensible design than could be achieved
> with inheritance and polymorphism.
> 
> I installed the 'sp' package, because I read that the Spatial Class is an
> abstract class, but I don't know where to look for the file where that
> class lives. I tried, among others, the files in:
> R/i486-pc-linux-gnu-library/2.9/sp/R.
> 
> Cheers!!
> 
> Albert-Jan
> 

It looks like you were looking in the R library where R stores sp after
installing it- the problem with this is that R converts all the code to a
binary format and stores it in a single file.  You want to download the
source tarball from CRAN:

  http://cran.r-project.org/web/packages/sp/index.html

Untar it and look in the R directory of the resulting folder.  You will see
a file called Class-Spatial.R that contains the S4 class definition.

Another good study in S4 inheritance is the Matrix package which is now
included in the R core.  You can download it's source from:

  http://cran.r-project.org/web/packages/Matrix/index.html

Look at the file called AllClass.R


Hope this helps!

-Charlie

-----
Charlie Sharpsteen
Undergraduate-- Environmental Resources Engineering
Humboldt State University
-- 
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