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Thread Subject:
Selecting Starting values in fsolve( ) function.

Subject: Selecting Starting values in fsolve( ) function.

From: eee S.D.

Date: 13 Nov, 2011 18:28:10

Message: 1 of 4

Hi.. Any body know.. how to select starting values.. in using fsolve() function.. to solve two non linear function..

Kindly help in this regard..

Thank you,

Subject: Selecting Starting values in fsolve( ) function.

From: Greg Heath

Date: 13 Nov, 2011 19:48:53

Message: 2 of 4

On Nov 13, 1:28 pm, "eee S.D." <dushy.i...@gmail.com> wrote:
> Hi.. Any body know..  how to select starting values.. in using fsolve() function.. to solve two non linear function..
>
> Kindly help in this regard..
>
> Thank you,

If you have two unknowns you can

1. Try to eliminate one and plot the remaining 1-D function
to find zeros.
2. Plot contours on rectangular grids to find simultaneous zeros.

Hope this helps.

Greg

Subject: Selecting Starting values in fsolve( ) function.

From: eee S.D.

Date: 14 Nov, 2011 04:44:13

Message: 3 of 4

Greg Heath <heath@alumni.brown.edu> wrote in message <1cc3e76e-5e51-427c-a9d5-9e575f070afa@u9g2000vbx.googlegroups.com>...
> On Nov 13, 1:28 pm, "eee S.D." <dushy.i...@gmail.com> wrote:
> > Hi.. Any body know..  how to select starting values.. in using fsolve() function.. to solve two non linear function..
> >
> > Kindly help in this regard..
> >
> > Thank you,
>
> If you have two unknowns you can
>
> 1. Try to eliminate one and plot the remaining 1-D function
> to find zeros.
> 2. Plot contours on rectangular grids to find simultaneous zeros.
>
> Hope this helps.
>
> Greg

Thanks for your reply..

But, Two equations what i have are complex non linear functions of two variables.. it is not
possible to eliminate any one of them.. unless i make too much approximation..

It has many solutions.. i am getting different solutions for each different starting values.. for
some starting values.. answer is same..

Is it the correct way..? which i am following.


Thank you..

Dush

Subject: Selecting Starting values in fsolve( ) function.

From: Roger Stafford

Date: 14 Nov, 2011 05:53:08

Message: 4 of 4

"eee S.D." <dushy.iitd@gmail.com> wrote in message <j9q6at$igt$1@newscl01ah.mathworks.com>...
> But, Two equations what i have are complex non linear functions of two variables.. it is not
> possible to eliminate any one of them.. unless i make too much approximation..
>
> It has many solutions.. i am getting different solutions for each different starting values.. for
> some starting values.. answer is same..
- - - - - - - - - -
  If you are finding numerous different (and valid!) solutions, then that is the nature of your equations and no technique is going to eliminate this multiplicity. It is something you must deal with.

  I doubt if any very effective suggestions to your problem can be made in this thread without your exhibiting in detail the two equations you are faced with. It would be helpful if you use very short, preferably one- or two-character, variable and parameter names, and if you combine parameters wherever possible so that the equations can be expressed in as compact a form as possible.

Roger Stafford

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