fsolve for nonlinear system

[Bart Vandewoestyne]

Hello all,

I'm trying to solve a nonlinear system using fsolve.  I'm using
Octave 3.2.2 on Windows and I'm following the PDF docs for this
version of Octave (the PDF that come installed together with
Octave 3.2.2 on Windows).

I define my function as:

  function y = f_3d(x)
  
  y(1) = 16*x(1)^4 + 16*x(2)^4 + x(3)^4 - 16;
  y(2) =    x(1)^2 +    x(2)^2 + x(3)^2 - 3;
  y(3) =    x(1)^3 -    x(2);

then I also create my Jacobian as:

  function J = jac_3d(x)
  
  J = zeros(3,3);
  J = [64*x(1)^3 64*x(2)^3 4*x(3)^3; ...
        2*x(1)    2*x(2)   2*x(3);   ...
        3*x(1)^2   -1      0];

If i don't use the Jacobian, then all works well:

  > x = [0.8; 0.6; 1.3];
  octave-3.2.2.exe:9:C:\Octave\3.2.2_gcc-4.3.0\bin
  > [x, fval, info] = fsolve(@f_3d, x0)
  x =
  
     0.87797
     0.67676
     1.33086
  
  fval =
  
    9.2213e-008  1.9237e-009  1.7637e-009
  
  info =  1

But if I try to use my own Jacobian i get errors:

  > [x, fval, info] = fsolve(address@hidden, @jac_3d}, x0)
  error: subscript indices must be either positive integers or logicals.
  error: called from:
  error:   C:\Octave\3.2.2_gcc-4.3.0\share\octave\3.2.2\m\optimization\fsolve.m 
at
   line 177, column 6


Can somebody tell me what I'm doing wrong here?  I can't see a difference
between what I do and the manual...

Kind regards,
Bart

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        "Share what you know.  Learn what you don't."