[R-sig-dyn-mod] Jacobian in compiled code

[John Harrold]

Hello,

I'll start by saying that I'm relatively new to R. I'm trying to solve ODEs
using compiled code. I'm generating automation tools (creating the same
system in several formats including R-scrpt and the C code needed for R to
run compiled code, and right now it's not feasible for me to generate the
Jacobian right now. As I understand it, the Jacobian is used by some
solvers but I don't believe it's required (at least not by most of them).
Is it possible to write compiled code with only the ODEs specified? I've
done this in Matlab with C and their mex functionality. If it's possible,
can someone briefly describe what I'd have to change in one of the examples
in the vignette on writing code in compiled languages:

R Package deSolve, Writing Code in Compiled Languages
<http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0CCIQFjAA&url=http%3A%2F%2Fcran.r-project.org%2Fweb%2Fpackages%2FdeSolve%2Fvignettes%2FcompiledCode.pdf&ei=jcwlVfbbNoT8oAT4_4HQAw&usg=AFQjCNFvPvW2Il_E8OGhkB-AiZVFrouHmw&sig2=qlAopNEfWAq4PhQt_bmN7w&bvm=bv.90491159,d.cGU>

Specifically do I need the 'jac' function (from the C examples). Do I
delete it? To I have it return a specific value like 0.

Thanks
John

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