[R] nonlinear regression and Excel solver

[Mike Prager]

On Wednesday 14 January 2004 19:57, Kristian Omland wrote:
 >
[snip]
 >
 > Is Excel's Solver an adequate tool for numerical approximation in general
 > and nonlinear regression in particular? Or should I push on writing
 > S-Plus code?

 From what I've heard (and I know some expert users), Excel's solver is 
pretty good. It may need to be restarted several times to come to its final 
resting place.

However, despite their considerable visual appeal and ease of learning, 
there are significant drawbacks, in my opinion, to using spreadsheets for 
this type of work:

(1) You can't easily review your "source code" to see what is 
happening.  The operations are hidden in cell formulas, or even worse, in 
macros. These must be examined one at a time.

(2) There are no inherent loop structures.

(3) It's easy to change a formula when you just mean to change a data value.

(4) Expansion to a different dimensionality can be more bug-prone than with 
a programming language like R (or C or Fortran).

Of course, opinions vary.

 > Is anyone out there interested in assisting me with S-Plus code with the
 > potential payoff of collaboration on a publication in the ecological
 > literature?

I would be interested if not already overcommitted (and by a large factor).

 > Obviously, I would be equally enthused if an R user was interested in a
collaboration.

I do hope you will find someone.  Good luck with your research! (We all 
need it.)



-- 
Michael Prager
NOAA Center for Coastal Fisheries and Habitat Research
Beaufort, North Carolina  28516  USA
http://shrimp.ccfhrb.noaa.gov/~mprager/

NOTE: Opinions expressed are personal, not official. No government
endorsement of any product is made or implied.