# JuMP Objective coefficient writing
**URL:** https://discourse.julialang.org/t/jump-objective-coefficient-writing/101286
**Category:** Optimization (Mathematical)
**Created:** [July 7, 2023, 1:47am UTC](https://discourse.julialang.org/t/jump-objective-coefficient-writing/101286 "2023-07-07T01:47:23Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@Luiz\_Monteiro](https://discourse.julialang.org/u/Luiz_Monteiro)
#### Post date: [July 7, 2023, 1:47am UTC](https://discourse.julialang.org/t/jump-objective-coefficient-writing/101286/1 "2023-07-07T01:47:24Z")
Hi,
I am trying to write an objective using index for each element of an expression, just like a simple constraint (example: i, h, k in `@constraint(model1, con19B[i in V0_customer, h in Vstation, j in V0_customer, k in B], z1[i,h,j,k] <= y[h])`
However, I cant find how to do it. My example below is not working:
```julia
@objective(model1, Min, [g in VArc_dummy_length, k in Vdominante_length],
sum(x[Arc_dummy[g][1],Arc_dummy[g][2],Arc_dummy[g][3]]* Mtime[Arc_dummy[g][1],Arc_dummy[g][3]]))
+ sum(x[Arc_dominante_strg[k][1],Arc_dominante_strg[k][2],Arc_dominante_strg[k][3]]* Mtime[Arc_dominante_strg[k][1],Arc_dominante_strg[k][2]]
+ x[Arc_dominante_strg[k][1],Arc_dominante_strg[k][2],Arc_dominante_strg[k][3]]* Mtime[Arc_dominante_strg[k][2],Arc_dominante_strg[k][3]])
+ sum(Δ[Arc_dominante_strg[k][1],Arc_dominante_strg[k][2],Arc_dominante_strg[k][3]])
```
Thanks in advance
---
### Author:  [@odow](https://discourse.julialang.org/u/odow)
#### Post date: [July 7, 2023, 2:01am UTC](https://discourse.julialang.org/t/jump-objective-coefficient-writing/101286/2 "2023-07-07T02:01:24Z")
> write an objective using index for each element of an expression
Do you want to _sum_ these elements? Typically, JuMP models require a scalar objective value.
I think you want instead
```julia
@objective(
model1,
Min,
sum(
# ... stuff here ...
for g in VArc_dummy_length, k in Vdominante_length
)
)
```
---
### Author:  [@Luiz\_Monteiro](https://discourse.julialang.org/u/Luiz_Monteiro)
#### Post date: [July 7, 2023, 9:18pm UTC](https://discourse.julialang.org/t/jump-objective-coefficient-writing/101286/3 "2023-07-07T21:18:54Z")
Hi @odow , is not exactally to sum over those element index.
I want something like this ilustrative example:
Vtotal =[1, 2, 3, 4, 5]
Vstation = [4,5]
@variable(model1, x[i in Vtotal, h in Vstation, j in Vtotal], Bin)
V1 = [[1,5,2] [1,4,2],[2,5,1],[3,5,2]] #V1 is a subset of specific arcs index
#The objective function should sum only over the specific arcs index at V1
@objective(model1, Min, x[1,5,2] + x[1,4,2] + x[2,5,1] + [3,5,2])
---
### Author:  [@odow](https://discourse.julialang.org/u/odow)
#### Post date: [July 7, 2023, 9:49pm UTC](https://discourse.julialang.org/t/jump-objective-coefficient-writing/101286/4 "2023-07-07T21:49:50Z")
I don’t really understand how that example matches your previous example, but as a general rule, your objective should return a scalar. You can’t write something like:
```julia
@objective(model1, Min, [g in VArc_dummy_length, k in Vdominante_length], ... )
```
Your example would be perhaps:
```julia
Vtotal = [1, 2, 3, 4, 5]
Vstation = [4, 5]
V1 = [[1,5,2] [1,4,2],[2,5,1],[3,5,2]]
model = Model()
@variable(model, x[Vtotal, Vstation, Vtotal], Bin)
@objective(model, Min, sum(x[i,h,j] for (i,h,j) in V1]))
```
---
### Author:  [@Luiz\_Monteiro](https://discourse.julialang.org/u/Luiz_Monteiro)
#### Post date: [July 8, 2023, 7:03pm UTC](https://discourse.julialang.org/t/jump-objective-coefficient-writing/101286/5 "2023-07-08T19:03:54Z")
Thanks @odow ,
It worked!
I think my first example wasnt clear, sorry for that.