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## Precision of fsolve

 From: John W. Eaton Subject: Precision of fsolve Date: Tue, 22 Sep 1998 07:47:36 -0500 (CDT)

```On 22-Sep-1998, Daniel Tourde <address@hidden> wrote:

| I am using the function fsolve like this :
|
|   y(1) = 12*((x(3)*x(1))/2)/E - nlcoef(3);
|   y(2) = 12*((x(3)*x(2)+x(1)*x(4))/6)/E - nlcoef(4);
|   y(3) = 12*((P*x(3)/2+x(4)*x(2)+x(1)*x(5))/12)/E - nlcoef(5);
|   y(4) = 12*((P*x(4)/2+x(5)*x(2))/20)/E - nlcoef(6);
|   y(5) = 12*((P*x(5))/60)/E - nlcoef(7);
|
|
| Some of my nlcoef values are very small (between 1e-7 and 1e-10) and it
| happens that the solutions send back by fsolve can be wrong due to
| rounding and precision errors.
|
| My question is the following :
|
| How can I increase the precision of fsolve, how can I lower the

Try fsolve_options:

octave:1> fsolve_options

*** fsolve_options:

fsolve_options (KEYWORD, VALUE)

Set or show options for fsolve.  Keywords may be abbreviated
to the shortest match.

Options for fsolve include:

keyword                                  value
-------                                  -----

tolerance                                1.49012e-08

octave:2> fsolve_options ("tol", 1e-12)
octave:3> fsolve_options ("tol")
ans =  1.0000e-12

jwe

```