Solving Nonlinear Equations in MATLAB: Troubleshooting with fsolve Command

[fluidman]

Hi to everyone.I were to solve a nonlinear equations system consisting of two unknown parameters and two equations.I have written a Matlab m-file to define the functions in order to solve them by embeded fsolve Matlab command.But I end up with an error occurring on the command window, when i attempt to solve the equations by typing
>> x0=[0.0157;0.01585];
>> [x, functionvalue, control, feature]=fsolve('saumrd',x0);
where saumrd is the name of the m-file in which I defined the functions.The error occurred after typing the above script on command window is as follows:

Maximum number of function evaluations reached:
increase options.MaxFunEvals.

Is ther anyone who will comment on the error and guide me to overcome this proplem?Thanking you so much.

 

[Dr Transport]

Look at your documentation, you're not converging to an answer within the number of maximum iterations allowed by fsolve. Look in the fsolve.m file and increase options.MaxFunEvals.

 

[tacman]

Hi there,

It seems like you have encountered a common issue when using the fsolve command in MATLAB. The error you are receiving indicates that the maximum number of function evaluations has been reached, and the solver is unable to find a solution within the given number of evaluations.

One way to overcome this problem is to increase the number of function evaluations allowed by adjusting the options.MaxFunEvals parameter. You can do this by adding the following lines of code before calling the fsolve command:

options = optimset('MaxFunEvals', 1000); % or any other desired value
[x, functionvalue, control, feature] = fsolve('saumrd', x0, options);

This will allow the solver to perform more function evaluations and hopefully find a solution. You can also try changing other parameters such as options.TolFun and options.TolX to potentially improve the solver's performance.

Another potential solution is to try using a different solver, such as fminsearch or fmincon, which may be more suitable for your specific problem.

I hope this helps! Good luck with your nonlinear equations.