[R] Need Advice: Considering Converting a Package from S3 to S4

spencerg spencer.graves at prodsyse.com
Tue Aug 11 19:24:58 CEST 2009

Hi, Terry: 

      Thanks for the comments.  I too vastly prefer S3 to S4.  Your 
comparison is based on much greater experience than mine. 

      Could you please check the link you sent?  I couldn't get it to 

      Thanks again.

Terry Therneau wrote:
>  For 90 percent of what I do I strongly prefer the loose (S3) rather than the 
> rigid (S4) classes.  So I'm closer to Rolf.  My summary of S4 vs S3
> A large increment in 
>   1. nuisance to write
>   2. difficulty to debug
>   3. ability to write very obscure code 
>   4. design
> Gain
>   5. ability to direct automatic conversions
>   6. validate the contents of a class object
>   For simple objects 5 and 6 can be critical.  Consider a date for instance, 
> which will often be turned into a character, added or subtracted as a numeric, 
> plotted, etc.  Conversely, aspects of 1-4 are less worrisome for a simple 
> object, particularly #4: I have a reasonable chance of "getting it right" the 
> first time.
>   For a complex object such as the result of a coxph fit 
>   	fit <- coxph(Surv(time, status) ~ age + sex + treatment)
> #5 makes no sense at all: as.numeric(fit)???  Number 4 and 6 are really hard;
> after 15+ years of tuning I am still modifying the list of components in a coxph 
> object.  I know more about the computational aspects of Cox models than almost 
> anyone and still it's not enough.  Changes are harder with rigid classes.
>   With reference to #3 above, for your amusement, look at
>      www.netfunny.com/rhf/jokes/98/May/straustrup.html
> the key line (to me) being "..every C++ programmer feels bound by some mystic 
> promise to use every damm element of the languange on every project..."
> Terry T.
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> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

Spencer Graves, PE, PhD
President and Chief Operating Officer
Structure Inspection and Monitoring, Inc.
751 Emerson Ct.
San José, CA 95126
ph:  408-655-4567

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