Re: Passing parameters to fsolve function - new syntax?

[David Bateman]

Aivo Jürgenson wrote:

> Hello,
>
> I have a function f(x,a,b,c), which I would like solve for variable x, 
> so that f(x,a,b,c)=0, where a,b,c are parameters, which are known at 
> the time of solving.
>
> However, current fsolve function in Octave only supports one-variable 
> functions. I suppose there is a work-around to declare specific global 
> variables and then giving values to those variables before calling the 
> fsolve function, but this doesn't seem to be a clean way of organizing 
> this.
>
> The fsolve FIX in the octave-forge package seems to expand this 
> functionality, but I'm not able to compile it. Also, the status of 
> this FIX seems to be unclear, as in the development mailing list 
> message http://sourceforge.net/mailarchive/message.php?msg_id=11922522:
>
> Paul Kienzle, in May, 2005:
>
> > I have no interest in maintaining this function.  I am removing it from
> > the build system for now, and will purge it completely if nobody steps
> > forward to update it.
> >
> > IIRC, the purpose of this function is to pass extra arguments to
> > fsolve, but we can do this now with the new syntax:
> >
> >     @(x) f(x,a,b,c)
> >
> > - Paul
>
>
> Could somebody explain this new syntax? I would be happy to use this 
> new and official way of passing extra arguments to fsolve, but I'm not 
> been able to find any examples of doing it.
>
> Aivo Jürgenson, address@hidden

Aivo,

The new syntax is not supportted in the CVS. I wrote a patch to support 
it which was a huge hack, which you can find at

http://www.octave.org/mailing-lists/octave-maintainers/2004/627

together with the explanation of why this is the wrong way to go.. Note 
that the changes to "quad" were made. However daspk, dasrt, dassl, 
fsolve, lsode and odessa weren't converted as the resulting code is an 
ugly hack. The only real solution is to completely dump the existing 
mess for these functions and reimplement it removing the underlying 
fortran code.... So the workaround with global variables is the only way 
this can be done...

Regards
David

--

David Bateman                                address@hidden
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Parc Les Algorithmes, Commune de St Aubin    +33 1 69 35 77 01 (Fax) 
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