# how to do conditional statements using optimisation variables?

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NN on 4 May 2021
Commented: Julian on 21 Jul 2023
hi all, how can i perform logical comparison using optimisation variable ?
I have tried this below code for optimisation using optimisation variable PbattV , but getting error :
Cost = Costa.*(PbattV<=200) +Costb.*(PbattV>=200);
P1= dt*Cost'*PbattV;
P2=dt*Cost'*PbattV;
P=P1-P2;
prob.ObjectiveSense = 'minimize';
prob.Objective = P;
An error occurred while running the simulation and the simulation was terminated Caused by: times Please help if you have any suggestion
basically i need to check if Pbatt is positive or negative and accordingly i have to chose Cost and use it for objective function;
##### 1 CommentShow -1 older commentsHide -1 older comments
Julian on 21 Jul 2023
Hi NN, I wanted to ask If you have found a working solution for your problem?
Have you found a way to rewrite your Problem?

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### Accepted Answer

Walter Roberson on 4 May 2021
Cost = Costa.*(PbattV<=200) +Costb.*(PbattV>=200);
Optimization variables cannot be converted to logical values. The only time you can compare an optimization variable to a value is in constructing a constraint.
Give up on trying to code it in terms of comparison operators: you will not succeed.
If there is a solution, then it will involve using mathematical tricks such as sqrt(x^2)/x to get the sign(x)
##### 17 CommentsShow 15 older commentsHide 15 older comments
NN on 19 Aug 2021
Ok.Still when it doesnt support another function with conditional statements, or even constraints, i cant perform that operation.
I am thinking some other approach without considering sign change
Walter Roberson on 21 Aug 2021
When you have discontinuous derivatives, the alternative supported by MATLAB are:

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