Asked by Clarisha Nijman
on 14 Dec 2018

Hello,

Solving a min max constraint problem in matlab,is a part/function of my whole code. This function finds the optimal linear combination of the distributions, x and y such that it approximates z very good. The problem is that the code is terminated if the optimization problem cannot be solved. In that case I would like to use choose my own values for the optimal parameters.

So I wrote this part in the code:

%If the optimal solution is not found then:

if sum(OptArgum(1:2))<1

OptArgum(1)=0.5;

OptArgum(2)=0.5;

end

But It does not work. So now I am left with two questions:

1) Can you give me some suggestion for better code?

2) How can I add arguments to the code such as 'MaxFunEvals', 1000, 'Maxiter', 1000, such that the code is not terminated easily?

Thank you in advance

This is the code of my function:

function[OptArgum,v]=ModelParametersMinMax (x, y, z)

%This function finds the optimal linear combination of the distributions, x and y such that it approximates z very good. z=a*x+(1-a)*y

%input

% x =The pdf vector of process x

% y =The pdf vector of process y

% z =The pdf vector of all processes together

%output

%OptArgum=A vector that consist of three entrees all coefficients for x,y and z

%v =A linear combination of the x and y such that v can be approximated by: a*x+(1-a)*y

%Construction of the constraint matrix

Aleq=[];

bleq=[];

Aeq=[1 1 0];

beq=1;

%bound of the variables

lb=[0 0 0];

ub=[];

x0=0.1*rand(3,1);%initial guess

Cs=[x y -z];%coefficients of the objective function

% Solving the minmax constraint problem

[OptArgum, ~] = fminimax(@(x) Cs*x,x0,Aleq,bleq(:),Aeq,beq,lb,ub);

%If the optimal solution is not found then:

if sum(OptArgum(1:2))<1

OptArgum(1)=0.5;

OptArgum(2)=0.5;

end

v=OptArgum(1)*xPred + OptArgum(2)*xEstimatedRate;%approximation for z

end

Answer by Matt J
on 14 Dec 2018

Edited by Matt J
on 14 Dec 2018

Accepted Answer

options=optimoptions(@fminimax,__________);

% Solving the minmax constraint problem

[OptArgum, ~,~,exitflag] = fminimax(@(x) Cs*x,x0,Aleq,bleq(:),Aeq,beq,lb,ub,[],options);

%If the optimal solution is not found then:

if exitflag<=0

OptArgum(1)=0.5;

OptArgum(2)=0.5;

end

Clarisha Nijman
on 15 Dec 2018

Thanks Matt,

This is exactly what I need, if an optimal solution is not found the whole code stops running, but now I know how to prevent that. However, I have to study the exitflag options better.

kind regards

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## 1 Comment

## Matt J (view profile)

Direct link to this comment:https://it.mathworks.com/matlabcentral/answers/435840-how-to-continue-without-solution-min-max-constraint-problem#comment_650809

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