MATLAB: Fsolve accuracy

displayfsolveMATLABoptimization

Hi all,

I am fairly new to matlab so excuse my ignorance as this could be an easy problem.

I am using the fsolve function and it is working fine and it outputs my three parameters that I need. However all three numbers are limited to an accuracy of four decimal places which I would like to increase to 6 or even more.

Does anyone have any advice to help me improve the accuracy? This is a snapshot of the code…

Init_Guess = [0.05 0.02 0.0000406];

options=optimset('Display','iter','MaxIter',3000,'MaxFunEvals',3000, 'TolFun', 1.0e-12, 'TolX',1.0e-12);

Coeffs = fsolve(@Solution_1,Init_Guess,options)

As you can see with the Initial guess I am trying to force the code to increase the decimal places but it doesn't seem to want to do it.

Regards

John Mulvihill

Best Answer

My guess is that you are talking about what is displayed, as opposed to what is calculated. Try typing

>> format long

to see more digits in the output of the command window.

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MATLAB: Fmincon does not even try other points other than initial x0

wasn't fmincon supposed to try other values of x before getting to that final result?

No, fmincon is a gradient-based solver (unlike ga) so if x0 is feasible and the gradient there is already zero, then fmincon has no reason to try other points. Often this happens because you have discretization operations like round() or ceil() in your objective function, which make it locally flat almost everwhere. For example, this 1D function is locally flat at all points except the integers:

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>> fmincon(fun,1.5,[],[],[],[],0,5,[],opts)
ans =
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>> fmincon(fun,2.7,[],[],[],[],0,5,[],opts)
ans =
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>> fmincon(fun,3.99,[],[],[],[],0,5,[],opts)
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MATLAB: Format display in MATLAB R2007b

format long

Best Answer

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MATLAB: Fmincon does not even try other points other than initial x0

MATLAB: Format display in MATLAB R2007b

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