# Concatenation of NamedArrays while maintaining column names

**URL:** <https://discourse.julialang.org/t/concatenation-of-namedarrays-while-maintaining-column-names/89666>\
**Category:** General Usage\
**Created:** [November 2, 2022, 4:38pm UTC](https://discourse.julialang.org/t/concatenation-of-namedarrays-while-maintaining-column-names/89666 "2022-11-02T16:38:10Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![Filippati](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/filippati/32/46143_2.png) [@Filippati](https://discourse.julialang.org/u/Filippati)\
**Post date:** [November 2, 2022, 4:38pm UTC](https://discourse.julialang.org/t/concatenation-of-namedarrays-while-maintaining-column-names/89666/1 "2022-11-02T16:38:11Z")

</div>

Hello everyone, I am trying to figure out how to concatenate NamedArrays while maintaining column names.

```julia
using NamedArrays

countriesq = ["USq", "CNq", "JPq", "FRq", "BDq", "ITq", "UKq"]
countriesr = ["USr", "CNr", "JPr", "FRr", "BDr", "ITr", "UKr"]
q = NamedArray(zeros(138, 7))
r = NamedArray(zeros(138, 7))
setnames!(q, countriesq, 2)
setnames!(r, countriesr, 2)

```

If I do

```julia
z = hcat(r, q)

```

I get numbers 1:14 as column names instead of countriesq and countriesr names.

Thank you very much for your help.

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<div class="post-metadata">

**Author:** ![ParadaCarleton](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/paradacarleton/32/20005_2.png) [@ParadaCarleton](https://discourse.julialang.org/u/ParadaCarleton)\
**Post date:** [November 2, 2022, 7:11pm UTC](https://discourse.julialang.org/t/concatenation-of-namedarrays-while-maintaining-column-names/89666/2 "2022-11-02T19:11:51Z")

</div>

I’m not sure what problem’s causing this, or if NamedArrays.jl just doesn’t provide this feature (concatenating while preserving names), but [DimensionalData.jl](https://github.com/rafaqz/DimensionalData.jl) shouldn’t have this same problem.

---

<div class="post-metadata">

**Author:** ![aplavin](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/aplavin/32/222056_2.png) [@aplavin](https://discourse.julialang.org/u/aplavin)\
**Post date:** [November 2, 2022, 7:16pm UTC](https://discourse.julialang.org/t/concatenation-of-namedarrays-while-maintaining-column-names/89666/3 "2022-11-02T19:16:47Z")

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`NamedArrays.jl` don’t support keeping keys when concatenating: [Keeping names in \*cat · Issue #74 · davidavdav/NamedArrays.jl · GitHub](https://github.com/davidavdav/NamedArrays.jl/issues/74). The issue is related to potentially nonunique keys after the operation.

There are multiple keyed/named array implementations that support this though.  
For example, `AxisKeys.jl` do allow duplicate keys and arbitrary concatenation:

```julia
julia> using AxisKeys

julia> q = KeyedArray(rand(3, 2), (["USq", "CNq", "JPq"], 1:2))
2-dimensional KeyedArray(...) with keys:
↓ 3-element Vector{String}
→ 2-element UnitRange{Int64}
And data, 3×2 Matrix{Float64}:
           (1) (2)
  ("USq") 0.330996 0.455291
  ("CNq") 0.914666 0.335489
  ("JPq") 0.178773 0.990683

julia> r = KeyedArray(rand(3, 2), (["USq", "CNq", "JPq"], 1:2))
2-dimensional KeyedArray(...) with keys:
↓ 3-element Vector{String}
→ 2-element UnitRange{Int64}
And data, 3×2 Matrix{Float64}:
           (1) (2)
  ("USq") 0.600243 0.997009
  ("CNq") 0.887196 0.979967
  ("JPq") 0.171013 0.663274

julia> hcat(r, q)
2-dimensional KeyedArray(...) with keys:
↓ 3-element Vector{String}
→ 4-element Vector{Int64}
And data, 3×4 Matrix{Float64}:
           (1) (2) (1) (2)
  ("USq") 0.600243 0.997009 0.330996 0.455291
  ("CNq") 0.887196 0.979967 0.914666 0.335489
  ("JPq") 0.171013 0.663274 0.178773 0.990683

```