# Status of Distances.jl

**URL:** <https://discourse.julialang.org/t/status-of-distances-jl/16789>\
**Category:** General Usage\
**Created:** [October 25, 2018, 3:45pm UTC](https://discourse.julialang.org/t/status-of-distances-jl/16789 "2018-10-25T15:45:38Z")\
**Posts on this page:** 7\
**Page:** 1

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**Author:** ![essenciary](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/essenciary/32/210469_2.png) [@essenciary](https://discourse.julialang.org/u/essenciary)\
**Post date:** [October 25, 2018, 3:45pm UTC](https://discourse.julialang.org/t/status-of-distances-jl/16789/1 "2018-10-25T15:45:38Z")

</div>

Is the package supposed to work on Julia v1? I see a commit about support for v0.7 but I get an error:

```julia
julia> movies[1,:]
9-element Array{Any,1}:
  "Moonlight (2016)"
 0
 0
 0
 1
 0
 0
 0
 0

julia> nemo
9-element Array{Any,1}:
  "Finding Nemo (2003)"
 0
 1
 1
 0
 1
 0
 0
 0

julia> hamming(movies[1,:], nemo)
ERROR: MethodError: no method matching one(::Type{Any})
Closest candidates are:
  one(::Type{Union{Missing, T}}) where T at missing.jl:83
  one(::Missing) at missing.jl:79
  one(::BitArray{2}) at bitarray.jl:392
  ...
Stacktrace:
 [1] one(::Type{Any}) at ./missing.jl:83
 [2] result_type(::Hamming, ::Array{Any,1}, ::Array{Any,1}) at /Users/adrian/.julia/packages/Distances/nLAdT/src/metrics.jl:194
 [3] eval_start(::Hamming, ::Array{Any,1}, ::Array{Any,1}) at /Users/adrian/.julia/packages/Distances/nLAdT/src/metrics.jl:196
 [4] evaluate at /Users/adrian/.julia/packages/Distances/nLAdT/src/metrics.jl:159 [inlined]
 [5] hamming(::Array{Any,1}, ::Array{Any,1}) at /Users/adrian/.julia/packages/Distances/nLAdT/src/metrics.jl:240
 [6] top-level scope at none:0

```

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<div class="post-metadata">

**Author:** ![foobar\_lv2](https://avatars.discourse-cdn.com/v4/letter/f/ee59a6/32.png) [@foobar\_lv2](https://discourse.julialang.org/u/foobar_lv2)\
**Post date:** [October 25, 2018, 4:04pm UTC](https://discourse.julialang.org/t/status-of-distances-jl/16789/2 "2018-10-25T16:04:11Z")

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Distances.jl is working fine on 1.0. I think this is simply a bug; you can work around it by

```julia
julia> Distances.result_type(::Hamming, ::AbstractArray{T1,N} where {T1,N}, ::AbstractArray{T2,N} where {T2,N})=Int

```

In reality, Hamming probably wants a separate implementation anyway. Desired handling of `NaN` and `missing` is not entirely obvious though.

```julia
julia> using Random, BenchmarkTools, Distances
julia> a=bitrand(10^5); b = bitrand(10^5);
julia> @btime evaluate($Hamming(), $a, $b);
  154.316 μs (1 allocation: 16 bytes)
julia> _fhamming(a,b) = count(a.==b);
julia> @btime _fhamming($a, $b);
  2.351 μs (2 allocations: 12.41 KiB)
julia> _fhamming(a,b) = count(isequal.(a,b));
julia> @btime _fhamming($a, $b);
  328.005 μs (3 allocations: 16.59 KiB)

```

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<div class="post-metadata">

**Author:** ![essenciary](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/essenciary/32/210469_2.png) [@essenciary](https://discourse.julialang.org/u/essenciary)\
**Post date:** [October 25, 2018, 4:15pm UTC](https://discourse.julialang.org/t/status-of-distances-jl/16789/3 "2018-10-25T16:15:43Z")

</div>

Thank you, this pointed me in the right direction. It doesn’t like the types of the arrays (it used to work fine in 0.6).

Ex:

```julia
julia> hamming(x,y)
ERROR: MethodError: no method matching one(::Type{Any})
Closest candidates are:
  one(::Type{Union{Missing, T}}) where T at missing.jl:83
  one(::Missing) at missing.jl:79
  one(::BitArray{2}) at bitarray.jl:392
  ...
Stacktrace:
 [1] one(::Type{Any}) at ./missing.jl:83
 [2] result_type(::Hamming, ::Array{Any,1}, ::Array{Any,1}) at /Users/adrian/.julia/dev/Distances/src/metrics.jl:194
 [3] eval_start(::Hamming, ::Array{Any,1}, ::Array{Any,1}) at /Users/adrian/.julia/dev/Distances/src/metrics.jl:196
 [4] evaluate at /Users/adrian/.julia/dev/Distances/src/metrics.jl:159 [inlined]
 [5] hamming(::Array{Any,1}, ::Array{Any,1}) at /Users/adrian/.julia/dev/Distances/src/metrics.jl:240
 [6] top-level scope at none:0

julia> hamming(Int[x...],Int[y...])
4

```

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<div class="post-metadata">

**Author:** ![foobar\_lv2](https://avatars.discourse-cdn.com/v4/letter/f/ee59a6/32.png) [@foobar\_lv2](https://discourse.julialang.org/u/foobar_lv2)\
**Post date:** [October 25, 2018, 4:24pm UTC](https://discourse.julialang.org/t/status-of-distances-jl/16789/4 "2018-10-25T16:24:01Z")

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But really, the above is not a reliable fix.

I’m not sure about the intended semantics for `missing` and `NaN`, but you the above fix will run into trouble with missing values. And the bitarray variant (count broadcasted `==`) is also bad; the real solution is to implement a specialization for `bitarray` (because that’s the main use for hamming distance).

Can you open an issue for this?

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<div class="post-metadata">

**Author:** ![essenciary](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/essenciary/32/210469_2.png) [@essenciary](https://discourse.julialang.org/u/essenciary)\
**Post date:** [October 25, 2018, 4:30pm UTC](https://discourse.julialang.org/t/status-of-distances-jl/16789/5 "2018-10-25T16:30:35Z")

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Sure!

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<div class="post-metadata">

**Author:** ![essenciary](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/essenciary/32/210469_2.png) [@essenciary](https://discourse.julialang.org/u/essenciary)\
**Post date:** [October 25, 2018, 4:34pm UTC](https://discourse.julialang.org/t/status-of-distances-jl/16789/6 "2018-10-25T16:34:04Z")

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I’m afraid I don’t understand the internals so feel free to expand on this if necessary:  
[https://github.com/JuliaStats/Distances.jl/issues/114](https://github.com/JuliaStats/Distances.jl/issues/114)

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<div class="post-metadata">

**Author:** ![kristoffer.carlsson](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/kristoffer.carlsson/32/22_2.png) [@kristoffer.carlsson](https://discourse.julialang.org/u/kristoffer.carlsson)\
**Post date:** [October 26, 2018, 3:55pm UTC](https://discourse.julialang.org/t/status-of-distances-jl/16789/7 "2018-10-26T15:55:05Z")

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[https://github.com/JuliaStats/Distances.jl/issues/114#issuecomment-433129061](https://github.com/JuliaStats/Distances.jl/issues/114#issuecomment-433129061) for why this worked on 0.6 and not 0.7 (spoiler: 0.6 optimization bug).