[R] Finding code for R functions

[Berton Gunter]

See chapter 5 on object oriented programming in the R language definition
manual. Also the  ?UseMethod man page. These will explain R's (S3) method
dispatch procedures.

Finally, search on CRAN for the R New newsletter article on namespaces,
which is where you'll find info on why you can't "see" certain functions.
See ?getAnywhere to learn how to see code for functions in namespaces.

-- Bert Gunter
Genentech Non-Clinical Statistics
South San Francisco, CA
 
"The business of the statistician is to catalyze the scientific learning
process."  - George E. P. Box
 
 

> -----Original Message-----
> From: r-help-bounces at stat.math.ethz.ch 
> [mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of Wolfrum, Ed
> Sent: Tuesday, October 18, 2005 2:27 PM
> To: r-help at stat.math.ethz.ch
> Subject: [R] Finding code for R functions
> 
> Greetings,
> 
> I am trying to figure out how to find the source code for R 
> functions. I
> am specifically interested in finding the code for the "prcomp"
> function. I know that typing the function name without 
> parenthesis will
> lead to the code (or to a .Internal or .FORTRAN or .C  call). 
> However, I
> don't really understand what is going on. For example, typing "mean"
> gives a "UseMethod" response, while typing "mean.default" give the
> actual code:
> 
> > mean
> function (x, ...) 
> UseMethod("mean")
> <environment: namespace:base>
> 
> > mean.default
> function (x, trim = 0, na.rm = FALSE, ...) 
> ---SNIP---
> }
> <environment: namespace:base>
> 
> Why is this? What does "mean.default" mean? I tried the same 
> thing with
> "prcomp". With the stats package loaded, I cannot get to the 
> source code
> for "prcomp".
> 
> > require(stats)
> [1] TRUE
> > prcomp
> function (x, ...) 
> UseMethod("prcomp")
> <environment: namespace:stats>
> > prcomp.default
> Error: object "prcomp.default" not found
>  
> How do I find the prcomp code? Are there general rules for finding the
> source code for functions that I should know?
> 
> Thanks in Advance,
> 
> Edward J. Wolfrum, Ph.D.
> National Renewable Energy Laboratory
> Golden, Colorado
> 
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