# Generating \`Array\` of random values from \`Array\` of Distributions

**URL:** <https://discourse.julialang.org/t/generating-array-of-random-values-from-array-of-distributions/5310>\
**Category:** Statistics\
**Tags:** question\
**Created:** [August 9, 2017, 6:24pm UTC](https://discourse.julialang.org/t/generating-array-of-random-values-from-array-of-distributions/5310 "2017-08-09T18:24:09Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![jacobcvt12](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/jacobcvt12/32/2695_2.png) [@jacobcvt12](https://discourse.julialang.org/u/jacobcvt12)\
**Post date:** [August 9, 2017, 6:24pm UTC](https://discourse.julialang.org/t/generating-array-of-random-values-from-array-of-distributions/5310/1 "2017-08-09T18:24:09Z")

</div>

I have an Array (of arbitary size) containing the parameters corresponding to the parameters of a distribution. In this example, the `Array` has size `(4, 3, 2)` but could e.g. be size `(3, 2)` or `(5, 2, 3, 2)`, etc.

For example,

```julia
using Distributions, StatsFuns
srand(1)
# pars[:, :, 1] correspond to mean
# pars[:, :, 2] correspond to standard deviation
pars = rand(Normal(), 4, 3, 2) 

pars[:, :, 2] = softplus.(pars[:, :, 2]) # put standard deviations on positive scale

# sample from normal distribution 
n = 2 # number of samples to draw from each Normal
rand.(Normal.(pars[:, :, 1], pars[:, :, 2]), n)
4×3 Array{Array{Float64,1},2}:
 [0.237169, 1.56555] [-0.866088, -0.343568] [0.319532, 0.475234]
 [0.34833, 0.0352314] [0.400087, 0.430776] [0.513749, 0.830742]
 [-1.71771, -0.646454] [2.58106, 1.80743] [2.46338, 1.99188]
 [-0.120796, -1.42402] [-2.5226, -2.96022] [1.17088, -0.0516749]

```

This gives me a an `Array` of `Array`s. What I would like is a `4x3xn` `Array`. How can I go about reshaping this `Array`?

---

<div class="post-metadata">

**Author:** ![Nosferican](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/nosferican/32/9275_2.png) [@Nosferican](https://discourse.julialang.org/u/Nosferican)\
**Post date:** [August 9, 2017, 11:45pm UTC](https://discourse.julialang.org/t/generating-array-of-random-values-from-array-of-distributions/5310/2 "2017-08-09T23:45:30Z")

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I will assume you meant to have the first values of each element in the array part of the `Matrix` in the first element along the third dimension and the second element as such. If that is the case you can do:

```julia
output = Array{Float64}(4,3,n)
for idx in 1:n
    output[:,:,idx] = map(elem -> elem[idx], array)
end
output
4×3×2 Array{Float64,3}:
[:, :, 1] =
  0.237169 -0.866088 0.319532
  0.34833 0.400087 0.513749
 -1.71771 2.58106 2.46338 
 -0.120796 -2.5226 1.17088 

[:, :, 2] =
  1.56555 -0.343568 0.475234 
  0.0352314 0.430776 0.830742 
 -0.646454 1.80743 1.99188  
 -1.42402 -2.96022 -0.0516749

```