[R] printing difftime summary

[David Winsemius]

On Nov 23, 2012, at 12:35 PM, Sam Steingold wrote:

>> * R. Michael Weylandt <zvpunry.jrlynaqg at tznvy.pbz> [2012-11-23  
>> 09:13:36 +0000]:
>>
>>> 2. because difftime.summary returns a data.frame and not a
>>> "Classes 'summaryDefault', 'table'" as I assume summary must return.
>>
>> See http://cran.r-project.org/doc/FAQ/R-FAQ.html#How-should-I-write-summary-methods_003f
>
> what are the requirements on the class summary.foo?

I'm not sure it makes sense to frame the question this way.  
summary.foo would nt be a class but rather a 'summary' method/function  
that applied to items of class 'foo.
>
> does it have to inherit from some other class?

There is implicit inheritance from the vector "class" and sometimes  
default methods will assume a numeric vector. But if you defin an  
object to be of a particular class, it would not need to have an  
explicit inheritance defined/

> how do I define a class?

That's pretty easy. Read:

?class         # and the pages to which it links.

(And also read ?methods, and the pages to which it links. Then read  
Sect 5 Object-oriented programming in the "R Language Definition".)

--

David Winsemius, MD
Alameda, CA, USA