[R] R function calling: efficiency of different alternatives

[Barry Rowlingson]

Ramon Diaz wrote:

> I think I recall reading something about differences in efficiency between 
> those three approaches, but I can't find the information (I've searched the 
> email archives, Venables & Ripley's "S programming" and MASS, the R manuals, 
> and Burn's "S Poetry"). 
> 
> Are there any real performance differences? 
> 

  I've always worked on the understanding that you should get code 
working and then profile it before you think about optimising it. 
There's no point worrying about efficiency issues with function calling 
strategies if your program is going to be spending 99% of its time doing 
those matrix operations and svd calculations.

  Do you think the overhead in searching for a function in a few tables, 
passing some parameters, and returning, is going to overwhelm the time 
taken in all the other calculations? Seems unlikely to me.

  Get it working one way or another - preferably with concerns in other 
aspects of software engineering (modularity, reusability etc) - and then 
if efficiency is a problem then profile the code to see where its 
spending its time. If it really is in the function calling mechanism, 
and not the guts of the code, then worry.

Barry