[R] open source and R

[Prof Brian Ripley]

On Sun, 13 Nov 2005 Ted.Harding at nessie.mcc.ac.uk wrote:

[...]

> There is one aspect though where R users are in the cold when
> it comes to C and FORTAN. If you want to understand the function
> 'eigen', say, then you can "?eigen" to learn about its usage.
> You can enter "eigen" to see the R code, and indeed that is
> not too imcomprehensible. But then you find
>
>  .Fortran("ch", n, n, xr, xi, values = dbl.n,
>           !only.values, vectors = xr, ivectors = xi, dbl.n,
>           dbl.n, double(2 * n), ierr = integer(1),
>           PACKAGE = "base")
>
> and similar for "rs", "cg" and "rg". Where's the help for
> these? Nowhere obvious! In fact you have to go to the source
> code, locate the FORTRAN routines, and study these, hoping
> that enough helpful comments have been included to steer
> your study. So it is a much more formidable task, especially
> if you are having to learn the language at the same time.

That is an unfair comment.  The help page for eigen explains what 
routines are used and gives you references to books describing them.
So the help _is_ in the most obvious place.

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595