R help - Apr 2011 - Help with objects

Hi all,

I would appreciate some help in understanding how to find out about objects.
For example, to the extent that I understand R it seems to treat everything
as an object even without declaring them as objects. Everything has
attributes, for example, which are like instance variables in objects. In
addition, there are S3 and S3 category objects.  Is there a good
introductory description of how these are different from standard R objects
and how they are different from each other?

Also, how does one find out more about how objects are declared. For
example, Data Mining with
R<http://www.liaad.up.pt/~ltorgo/DataMiningWithR/code3.html>uses the
quantmod package. I am used to Java's JavaDoc where one can see how
classes are declared, what the instance variables and methods are, etc. I
don't see anything similar for this package.  How, for example, would one
find out what the instance variables are in a quantmod object and what the
methods are that are defined on quantmod objects? I know that there is the
standard quantmod documentation, but that doesn't seem
to distinguish between standard functions and class-based methods. Nor, as
far as I can see, does it describe the instance variables in a quantmod
object.

Thanks.

*-- Russ Abbott*
*_____________________________________________*
***  Professor, Computer Science*
*  California State University, Los Angeles*

*  Google voice: 747-*999-5105
*  blog: *http://russabbott.blogspot.com/
  vita:  http://sites.google.com/site/russabbott/
*_____________________________________________*

	[[alternative HTML version deleted]]

Russ Abbott wrote:
> Hi all,
> 
> I would appreciate some help in understanding how to find out about
objects.
> For example, to the extent that I understand R it seems to treat everything
> as an object even without declaring them as objects.
That's correct.

  Everything has
> attributes, for example, which are like instance variables in objects.
That's not quite true.  There are a few special kinds of objects which 
can't have attributes.  The NULL object is the only one you're likely to
meet in regular code.

  In
> addition, there are S3 and S3 category objects.  Is there a good
> introductory description of how these are different from standard R objects
> and how they are different from each other?
S3 and S4 are layers put on top of the regular system for handling 
objects.  S3 objects just have a class attribute, which causes some 
functions to handle them specially; this is introduced in An 
Introduction to R, and more fully described in the R Language 
Definition.  S4 is a more complex system, partly described in the 
?Methods help topic, more completely in the references listed on that page.

Duncan Murdoch
> Also, how does one find out more about how objects are declared. For
> example, Data Mining with
> R<http://www.liaad.up.pt/~ltorgo/DataMiningWithR/code3.html>uses the
> quantmod package. I am used to Java's JavaDoc where one can see how
> classes are declared, what the instance variables and methods are, etc. I
> don't see anything similar for this package.  How, for example, would
one
> find out what the instance variables are in a quantmod object and what the
> methods are that are defined on quantmod objects? I know that there is the
> standard quantmod documentation, but that doesn't seem
> to distinguish between standard functions and class-based methods. Nor, as
> far as I can see, does it describe the instance variables in a quantmod
> object.
> 
> Thanks.
> 
> *-- Russ Abbott*
> *_____________________________________________*
> ***  Professor, Computer Science*
> *  California State University, Los Angeles*
> 
> *  Google voice: 747-*999-5105
> *  blog: *http://russabbott.blogspot.com/
>   vita:  http://sites.google.com/site/russabbott/
> *_____________________________________________*
> 
> 	[[alternative HTML version deleted]]
> 
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