# How to get unique values of list of struct based on condition?

**URL:** <https://discourse.julialang.org/t/how-to-get-unique-values-of-list-of-struct-based-on-condition/84678>\
**Category:** General Usage\
**Tags:** question\
**Created:** [July 23, 2022, 3:27pm UTC](https://discourse.julialang.org/t/how-to-get-unique-values-of-list-of-struct-based-on-condition/84678 "2022-07-23T15:27:46Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![Phuntsho](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/phuntsho/32/46546_2.png) [@Phuntsho](https://discourse.julialang.org/u/Phuntsho)\
**Post date:** [July 23, 2022, 3:27pm UTC](https://discourse.julialang.org/t/how-to-get-unique-values-of-list-of-struct-based-on-condition/84678/1 "2022-07-23T15:27:46Z")

</div>

I have a list of struct as shown

```julia
struct probs
    A::Tuple{Int64, Int64}; C::Tuple{Int64, Int64}; Cost::Int64
end
pop_vect = [probs((rand(1:20),rand(1:20)),(rand(1:20),rand(1:20)), rand(1:20)) for i = 1:100]

```

Now I want to get unique values of `pop_vect` so that the Cost is unique.

```julia
unique(pop_vect)

```

doesn’t help at all. Thanks for help in advance.

---

<div class="post-metadata">

**Author:** ![liamfdoherty](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/liamfdoherty/32/24516_2.png) [@liamfdoherty](https://discourse.julialang.org/u/liamfdoherty)\
**Post date:** [July 23, 2022, 3:44pm UTC](https://discourse.julialang.org/t/how-to-get-unique-values-of-list-of-struct-based-on-condition/84678/2 "2022-07-23T15:44:30Z")

</div>

If I understand your question correctly, this should do what you are expecting:

```julia
unique(prob -> prob.Cost, pop_vect)

```

This applies the function in the first argument (i.e., checking the cost) to the vector `pop_vect` and then returns all unique elements based on the output of that function.

---

<div class="post-metadata">

**Author:** ![liamfdoherty](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/liamfdoherty/32/24516_2.png) [@liamfdoherty](https://discourse.julialang.org/u/liamfdoherty)\
**Post date:** [July 23, 2022, 4:20pm UTC](https://discourse.julialang.org/t/how-to-get-unique-values-of-list-of-struct-based-on-condition/84678/3 "2022-07-23T16:20:57Z")

</div>

On second thought, I may have misunderstood what you are looking for. It is possible that what you are expecting is something along the lines of

```julia
function isonly(obj, itr)
    return count(x -> x == obj, itr) == 1
end

costs = [prob.Cost for prob in pop_vect]
answers = [prob for prob in pop_vect if isonly(prob.Cost, costs)]

```

The previous solution gives one instance of _each_ cost, but this instead gives the list of elements of `pop_vect` for which the cost is the _only_ such cost. As an example, if you generated 10 samples

```julia
10-element Vector{probs}:
 probs((7, 12), (19, 7), 1)
 probs((4, 18), (18, 8), 6)
 probs((1, 1), (5, 1), 20)
 probs((18, 17), (10, 8), 12)
 probs((20, 6), (14, 15), 15)
 probs((19, 19), (10, 6), 1)
 probs((19, 4), (3, 9), 15)
 probs((1, 15), (18, 20), 9)
 probs((10, 1), (1, 6), 8)
 probs((13, 5), (12, 20), 4)

```

the above code would return

```julia
6-element Vector{probs}:
 probs((4, 18), (18, 8), 6)
 probs((1, 1), (5, 1), 20)
 probs((18, 17), (10, 8), 12)
 probs((1, 15), (18, 20), 9)
 probs((10, 1), (1, 6), 8)
 probs((13, 5), (12, 20), 4)

```

Please check which of these solutions matches your desired behavior!