Re: Using fsolve to solve example problem from documentation gives very different result

[Doug Stewart]

On Wed, Oct 14, 2015 at 12:40 PM, Steven Davis <address@hidden> wrote:

Hi,

I was trying to use fsolve to solve a system of equations, and couldn't get it to work.  So I decided to try entering the example from the Octave documentation, Chapter 20 page 505. I figured once I got that to run I could work my way through to figure out what I was doing wrong.  But I couldn't get fsolve to give the same result the documentation example said I should get! 

I entered into the editor and saved as f.m the following:

function y=f(x)

y=zeros(2,1);

y(1)=-2*x(1)^2+3*x(1)*x(2)+4*sin(x(2))-6;

y(2)=3*x(1)^2-2*x(1)*x(2)^2+3*cos(x(1))+4;

endfunction

I then entered into the command window:

 [x,fval,info]=fsolve(@f,[1;2])

According to the documentation I should get:

x =

0.57983

2.54621

fval =

-5.7184e-10

5.5460e-10

info = 1

Instead I got:

I tried a copy and past from here and it worked

 ans =  1

x =

   0.57983

   2.54621

fval =

  -2.8991e-08

   4.9167e-07

info =  1

>>

So I think you have a different file named fsolve.m somewhere in your path.

Doug