Add sales constraint to model

[atakzltn]

Hi,

I want to add a new constraint to my optimization model. I work with omprt library. I have stores (j) and customers (i). I want to minimize transportation cost.

My model is same with your example:

MIPModel() %>%

add_variable(x[i, j], i = 1:n, j = 1:m, type = "binary") %>%

add_variable(y[j], j = 1:m, type = "binary") %>%

set_objective(sum_expr(transportcost(i, j) * x[i, j], i = 1:n, j = 1:m) + sum_expr(fixedcost[j] * y[j], j = 1:m), "min") %>%

add_constraint(sum_expr(x[i, j], j = 1:m) == 1, i = 1:n) %>%

add_constraint(x[i,j] <= y[j], i = 1:n, j = 1:m)

I want to add a new constraint. For example I have 30 different stores. First 10 stores have to sell minimum 15 units, second 20 stores have to sell minimum 10 units and third 30 stores have to sell 5 units.

I try to write like this but it didn't work:

add_constraint(sum_expr(y[j], j=1:30) >= 30, i = 1:n)

Please help!!!