Try using the @NLobjective macro:
@NLobjective(model, Min, sum(sum(x[i, j] for j in 1:J) for i in 1:N))
You should also read Please read: make it easier to help you and provide a minimal example of what you are trying to achieve.
Try using the @NLobjective macro:
@NLobjective(model, Min, sum(sum(x[i, j] for j in 1:J) for i in 1:N))
You should also read Please read: make it easier to help you and provide a minimal example of what you are trying to achieve.