how to get the index of the optimal value, of the objective function, obtained after cvx_end?
The optimal objective value is contained in cvx_optval after CVX has completed. You can save this into another MATLAB variable, including an array, if you want, such as
my_optimal_objective_value = cvx_optval.
If this is not what you want, please explain more clearly what you want to do. I don’t know what you mean by “index” of the optimal value of the objective function.