# Creating an Array of Distribution Objects

**URL:** <https://discourse.julialang.org/t/creating-an-array-of-distribution-objects/23736>\
**Category:** New to Julia\
**Created:** [May 1, 2019, 2:57pm UTC](https://discourse.julialang.org/t/creating-an-array-of-distribution-objects/23736 "2019-05-01T14:57:03Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![jbu](https://avatars.discourse-cdn.com/v4/letter/j/a8b319/32.png) [@jbu](https://discourse.julialang.org/u/jbu)\
**Post date:** [May 1, 2019, 2:57pm UTC](https://discourse.julialang.org/t/creating-an-array-of-distribution-objects/23736/1 "2019-05-01T14:57:03Z")

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I’m just getting started using Julia. My version is 1.0.3 on Ubuntu 16.04. I was trying to create an array of [Normal Distribution objects](https://juliastats.github.io/Distributions.jl/stable/starting.html) in the REPL using a for loop as follows:

```julia
using Distributions
means = 10*rand(10)
d = []
for j = 1:size(means,1)
       append!(d, Normal(means[j]))
end

```

However, the code threw the following error:

```julia
ERROR: MethodError: no method matching iterate(::Normal{Float64})
Closest candidates are:
  iterate(::Core.SimpleVector) at essentials.jl:589
  iterate(::Core.SimpleVector, ::Any) at essentials.jl:589
  iterate(::ExponentialBackOff) at error.jl:171
  ...
Stacktrace:
 [1] zip_iterate(::UnitRange{Int64}, ::Normal{Float64}, ::Tuple{}, ::Tuple{}) at ./iterators.jl:304
 [2] iterate at ./iterators.jl:320 [inlined]
 [3] _append!(::Array{Any,1}, ::Base.HasLength, ::Normal{Float64}) at ./array.jl:909
 [4] append!(::Array{Any,1}, ::Normal{Float64}) at ./array.jl:902
 [5] top-level scope at ./REPL[58]:2 [inlined]
 [6] top-level scope at ./none:0

```

Not quite sure what the problem is. Can Distribution objects not be stored in arrays?

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<div class="post-metadata">

**Author:** ![stillyslalom](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/stillyslalom/32/45687_2.png) [@stillyslalom](https://discourse.julialang.org/u/stillyslalom)\
**Post date:** [May 1, 2019, 3:02pm UTC](https://discourse.julialang.org/t/creating-an-array-of-distribution-objects/23736/2 "2019-05-01T15:02:25Z")

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If you’re adding a single item to an array, use `push!` instead of `append!` (which is meant for adding a collection to a preexisting collection). You could also write it as such:

```julia
julia> [Normal(μ) for μ in 10rand(10)]
10-element Array{Normal{Float64},1}:
 Normal{Float64}(μ=8.259182894319487, σ=1.0)  
 Normal{Float64}(μ=5.722960970066662, σ=1.0)  
 Normal{Float64}(μ=4.906795769403773, σ=1.0)  
 ...

```

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**Author:** ![Christopher\_Fisher](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/christopher_fisher/32/26132_2.png) [@Christopher\_Fisher](https://discourse.julialang.org/u/Christopher_Fisher)\
**Post date:** [May 1, 2019, 3:10pm UTC](https://discourse.julialang.org/t/creating-an-array-of-distribution-objects/23736/3 "2019-05-01T15:10:52Z")

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> [@stillyslalom](#):
>
> julia\> [Normal(μ) for μ in 10rand(10)] 10-element Array{Normal{Float64},1}: Normal{Float64}(μ=8.259182894319487, σ=1.0) Normal{Float64}(μ=5.722960970066662, σ=1.0) Normal{Float64}(μ=4.906795769403773, σ=1.0) …

This approach also has the benefit of being type stable, which will be more performant. Your type was `Array{Any,1}`, whereas the type above is `Array{Normal{Float64},1}`.

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<div class="post-metadata">

**Author:** ![jbu](https://avatars.discourse-cdn.com/v4/letter/j/a8b319/32.png) [@jbu](https://discourse.julialang.org/u/jbu)\
**Post date:** [May 1, 2019, 3:12pm UTC](https://discourse.julialang.org/t/creating-an-array-of-distribution-objects/23736/4 "2019-05-01T15:12:38Z")

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Excellent! Works perfectly, and much cleaner syntax. Thank you!