R devel - Nov 2008 - handling a matrix and .C

Hello R-devel,

I want to write extensions for R in C (maybe C++ and Fortran later) and it works
fine, but there is one problem, which I cannot solve (in my view).

I want to handle a matrix from R in C. For arrays there is
"as.double(...)", but nothing for a matrix.

I searched a while, but didn't find something.

Last I looked at the source code of e1071 and of the core itself and recognized
(I hope I understood this), that you (and the "e1071" people) use
"as.double()" and give ".C" an array and one have to
"parse" the matrix again in the C function.

This sounds a little complicate. Isn't there another way? A more adapted
way?

Greetings

Wilm

ps: I joined the R-devel list, but didn't get an confirmation mail. I hope
this is normal
--

> Last I looked at the source code of e1071 and of the core itself and
recognized (I hope I understood this), that you (and the "e1071"
people) use "as.double()" and give ".C" an array and one
have to "parse" the matrix again in the C function.
I think this is the simplest way to handle matrices at this level - after all a
matrix is really an homogenous array of data with indexing information ?

I have an example of handling matrices (using .Call) in an old post:

http://www.theresearchkitchen.com/blog/archives/113

Cheesr
Rory


***********************************************************************************
The Royal Bank of Scotland plc. Registered in Scotland No 90312. Registered
Office: 36 St Andrew Square, Edinburgh EH2 2YB.
Authorised and regulated by the Financial Services Authority 

This e-mail message is confidential and for use by the=2...{{dropped:22}}

You should not have started with R/C API without reading this (first
link in google): "Writing R Extensions". For your particular question
you want pages 72+ and sections 5.9.3 and 5.9.4, possibly further as
well

Dr Oleg Sklyar
Research Technologist
AHL / Man Investments Ltd
+44 (0)20 7144 3107
osklyar at maninvestments.com 
> -----Original Message-----
> From: r-devel-bounces at r-project.org 
> [mailto:r-devel-bounces at r-project.org] On Behalf Of Wilm Schumacher
> Sent: 24 November 2008 18:59
> To: r-devel at r-project.org
> Subject: [Rd] handling a matrix and .C
> 
> Hello R-devel,
> 
> I want to write extensions for R in C (maybe C++ and Fortran 
> later) and it works fine, but there is one problem, which I 
> cannot solve (in my view).
> 
> I want to handle a matrix from R in C. For arrays there is 
> "as.double(...)", but nothing for a matrix.
> 
> I searched a while, but didn't find something.
> 
> Last I looked at the source code of e1071 and of the core 
> itself and recognized (I hope I understood this), that you 
> (and the "e1071" people) use "as.double()" and give
".C" an
> array and one have to "parse" the matrix again in the C function.
> 
> This sounds a little complicate. Isn't there another way? A 
> more adapted way?
> 
> Greetings
> 
> Wilm
> 
> ps: I joined the R-devel list, but didn't get an confirmation 
> mail. I hope this is normal
> --
> 
> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
> 
**********************************************************************
Please consider the environment before printing this email or its attachments.

The contents of this email are for the named addressees ...{{dropped:19}}