# JuMP: vector variable to user defined NLobjective

**URL:** <https://discourse.julialang.org/t/jump-vector-variable-to-user-defined-nlobjective/11330>\
**Category:** Optimization (Mathematical)\
**Tags:** jump\
**Created:** [June 1, 2018, 10:41am UTC](https://discourse.julialang.org/t/jump-vector-variable-to-user-defined-nlobjective/11330 "2018-06-01T10:41:48Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![mrapo](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/mrapo/32/3911_2.png) [@mrapo](https://discourse.julialang.org/u/mrapo)\
**Post date:** [June 1, 2018, 10:41am UTC](https://discourse.julialang.org/t/jump-vector-variable-to-user-defined-nlobjective/11330/1 "2018-06-01T10:41:49Z")

</div>

I I’m trying to optimize an user defined function with JuMP. The variable is a vector of length 30.  
I’ve tried the following two ways to define the objective, but both of them throw an error.  
The first way I tried with the @eval -macro:

```
m = Model(solver = NLoptSolver(algorithm=:LD_SLSQP))
JuMP.register(m, :f, 1, f, autodiff = true)
n = 30
@variable(m, x[1:n])
for i in 1:n
    setvalue(x[i],x0[i])
end

@eval @NLobjective(m, Max, $(Expr(:call, :f, [Expr(:ref,:x,i) for i=1:n]...)))
status = solve(m)

Julia> ERROR: LoadError: Incorrect number of arguments for "f" in nonlinear expression.

```

The other way I tried with setNLobjective -function:

```
m = Model(solver = NLoptSolver(algorithm=:LD_SLSQP))
JuMP.register(m, :f, 1, f, autodiff = true)
n = 30 
@variable(m, x[1:n])
for i in 1:n
    setvalue(x[i],x0[i])
end 
JuMP.setNLobjective(m, :Min, Expr(:call, :f, [x[i] for i=1:n]...))
status = solve(m) 

Julia> ERROR: LoadError: KeyError: key :f not found

```

Anyone having a clue what I might be doing wrong here?

---

<div class="post-metadata">

**Author:** ![mrapo](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/mrapo/32/3911_2.png) [@mrapo](https://discourse.julialang.org/u/mrapo)\
**Post date:** [June 1, 2018, 10:53am UTC](https://discourse.julialang.org/t/jump-vector-variable-to-user-defined-nlobjective/11330/2 "2018-06-01T10:53:47Z")

</div>

I figured the problem was the number of variables on the line

```
JuMP.register(m, :f, 1, f, autodiff = true)

```

And that it should be

```
JuMP.register(m, :f, 30, f, autodiff = true)

```

Because x is a vector of length 30.