# Key 2 not found error

**URL:** <https://discourse.julialang.org/t/key-2-not-found-error/43105>\
**Category:** Optimization (Mathematical)\
**Created:** [July 15, 2020, 6:42am UTC](https://discourse.julialang.org/t/key-2-not-found-error/43105 "2020-07-15T06:42:54Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![mayar](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/mayar/32/16426_2.png) [@mayar](https://discourse.julialang.org/u/mayar)\
**Post date:** [July 15, 2020, 6:42am UTC](https://discourse.julialang.org/t/key-2-not-found-error/43105/1 "2020-07-15T06:42:54Z")

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Hello,

What does this error mean? “Key 2 not found”

```julia
Nodes_set=[1,2,3]
Gen_set=[1,3]
Pd=[0,-4,0]
JuMP.@variable(m, 0.1 ≤ p[i in Gen_set] ≤ 2)
JuMP.@variable(m, pij[i = Nodes_set, j = Nodes_set])
JuMP.@constraint(m, Pnodal[i in Nodes_set], sum(pij[i,j] for j = Nodes_set) == p[i]+Pd[i] )

```

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<div class="post-metadata">

**Author:** ![mayar](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/mayar/32/16426_2.png) [@mayar](https://discourse.julialang.org/u/mayar)\
**Post date:** [July 15, 2020, 6:43am UTC](https://discourse.julialang.org/t/key-2-not-found-error/43105/2 "2020-07-15T06:43:55Z")

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![e](https://global.discourse-cdn.com/julialang/original/3X/c/a/caf9fb502ad87469952fffd418bd7e3a6287fb8c.jpeg)

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<div class="post-metadata">

**Author:** ![tomerarnon](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/tomerarnon/32/3170_2.png) [@tomerarnon](https://discourse.julialang.org/u/tomerarnon)\
**Post date:** [July 15, 2020, 8:43am UTC](https://discourse.julialang.org/t/key-2-not-found-error/43105/3 "2020-07-15T08:43:48Z")

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Using your variable definitions:

```nohighlight

julia> p
1-dimensional DenseAxisArray{VariableRef,1,...} with index sets:
    Dimension 1, [1, 3]
And data, a 2-element Array{VariableRef,1}:
 p[1]
 p[3]

julia> Pd
3-element Array{Int64,1}:
  0
 -4
  0

julia> pij
2-dimensional DenseAxisArray{VariableRef,2,...} with index sets:
    Dimension 1, [1, 2, 3]
    Dimension 2, [1, 2, 3]
And data, a 3×3 Array{VariableRef,2}:
 pij[1,1] pij[1,2] pij[1,3]
 pij[2,1] pij[2,2] pij[2,3]
 pij[3,1] pij[3,2] pij[3,3]

```

Note that `p` doesn’t have index “2” because it is defined with `Gen_set`. When you use `i` to index it (along with `pij` and `Pd`) it fails when the index is 2.

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<div class="post-metadata">

**Author:** ![mayar](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/mayar/32/16426_2.png) [@mayar](https://discourse.julialang.org/u/mayar)\
**Post date:** [July 15, 2020, 10:30am UTC](https://discourse.julialang.org/t/key-2-not-found-error/43105/4 "2020-07-15T10:30:42Z")

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Thank you