[Rd] Problem with R math library.

[Dirk Eddelbuettel]

Salut Guilluame,

On 28 January 2010 at 12:38, Guillaume Yziquel wrote:
| Hello.
| 
| I've been working on my OCaml-R binding, and I quite pleased to see that 
| it is functional, though far from being perfect or polished. You can 
| find the gitweb webpage and the interface documentation at
| 
| 	http://yziquel.homelinux.org/gitweb/?p=ocaml-r.git;a=tree
| 	http://yziquel.homelinux.org/topos/api/ocaml-r/index.html
| 
| I'm having unexpected trouble with the math library, though. The 
| interface documentation is here:
| 
| 	http://yziquel.homelinux.org/topos/api/ocaml-r/Rmath.html
| 
| For instance, for the norm_rand symbol, I have the following 
| documentation comment:
| 
| > val norm_rand : unit -> float
| > Random variates from the standard normal distribution. Bug: currently systematically returns -8.77332116900134373.
| 
| Any idea as to why the function systematically returns the same value? 
| Is there a way the math library should be initialised?

I think it is pretty clearly documented in R-exts:

  6.3 Random number generation
  ============================
  
  The interface to R's internal random number generation routines is
  
       double unif_rand();
       double norm_rand();
       double exp_rand();
  
  giving one uniform, normal or exponential pseudo-random variate.
  However, before these are used, the user must call
  
       GetRNGstate();
  
  and after all the required variates have been generated, call
  
       PutRNGstate();
  
  These essentially read in (or create) `.Random.seed' and write it out
  after use.

Dirk

| 
| All the best,
| 
| -- 
|       Guillaume Yziquel
| http://yziquel.homelinux.org/
| 
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-- 
Three out of two people have difficulties with fractions.