MATLAB: Inequality Indexing using Optimization Toolbox

constrained optimizationoptimizationOptimization Toolboxoptimizationinequality

I would like to optimize an objective function with a constraint that is based on logical indexing. However, it seems like I can't just treat the optimization variable as I would a regular double. I was hoping for some advice about how to structure the constraint.
The code I have is written below. The variables A and B are n x 1 doubles and c is a scalar. So, I want to sum the values in A corresponding to indices for which the optimization variable x is greater than B. 
x = optimvar('x',n); % Creates optimization variable 
objfun = sum(x); % Creates objective function
constraint = sum(A(x>=B))>=c; % Constraint based on logical indexing
Thank you!

Best Answer

What Abdolkarim is getting it is the following, I believe. It requires known upper bounds U (vector or scalar) and lower bounds L on x. 
x = optimvar('x',n,'Lower',L,'Upper',U); 
e = optimvar('e',n,'Lower',0,'Upper',1,'type','integer');
 
Con.constr1 = e>=(x-B)./(U-B)/2;   % x>B ==> e=1
Con.constr2 = e<=1-(B-x)./(B-L)/2; % x<B ==> e=0
Con.constr3 = A(:).'*e>=c;
prob=optimproblem('Objective',sum(x),'Constraints', Con)
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