Why I got a waring

% Solve the system of equations starting at the point [0,0,0].

% PL = x(1); c = x(2); k = x(3);

% Initial guess is [0,0,0], you can change it accordingily

fun = @root2d;

x0 = [0,0,0];

x = fsolve(fun,x0)

Warning: Trust-region-dogleg algorithm of FSOLVE cannot handle non-square systems; using Levenberg-Marquardt algorithm instead.

No solution found.

fsolve stopped because the relative size of the current step is less than the

value of the step size tolerance, but the vector of function values

is not near zero as measured by the value of the function tolerance.

x = 1×3

1.0e+05 *

2.0192 -0.0000 0

function F = root2d(x)

F(1) = x(1) * exp(-x(2)*exp(-x(3)*0)) - 179323;

F(2) = x(1) * exp(-x(2)*exp(-x(3)*10)) - 203302;

F(2) = x(1) * exp(-x(2)*exp(-x(3)*20)) - 226542;

end

[Alex Sha]

Here are solution:

x1: 446505.431672108
x2: 0.912262916225994
x3: 0.0148006249649759

Answer 1

[Walter Roberson]

You write to F(2) twice.

The warning is because the default algorithm requires square outputs from your function, such as 1x1 or 2x2. You want three outputs so you need to use a different algorithm. It is automatically switching algorithms for you but warns you that your choosen algorithm was not used.