# Why \`sprand\` does not accept a Distribution arg?

**URL:** <https://discourse.julialang.org/t/why-sprand-does-not-accept-a-distribution-arg/127255>\
**Category:** General Usage\
**Tags:** distributions, sparsearrays\
**Created:** [March 22, 2025, 7:38am UTC](https://discourse.julialang.org/t/why-sprand-does-not-accept-a-distribution-arg/127255 "2025-03-22T07:38:30Z")\
**Posts on this page:** 11\
**Page:** 1

<div class="post-metadata">

**Author:** ![WalterMadelim](https://avatars.discourse-cdn.com/v4/letter/w/3e96dc/32.png) [@WalterMadelim](https://discourse.julialang.org/u/WalterMadelim)\
**Post date:** [March 22, 2025, 7:38am UTC](https://discourse.julialang.org/t/why-sprand-does-not-accept-a-distribution-arg/127255/1 "2025-03-22T07:38:30Z")

</div>

Hi there,  
I wonder why this cannot work out (What is the available method currently then?).

```julia
julia> import SparseArrays.sprand as sprand

julia> import Distributions.Uniform as UD

julia> sprand(5, 6, .7)
5×6 SparseArrays.SparseMatrixCSC{Float64, Int64} with 23 stored entries:
 0.213111 0.611876 0.592097 ⋅ ⋅ ⋅ 
 0.50981 0.326668 0.792674 0.227358 0.322273 0.616509
 0.9323 0.136838 0.56782 0.843999 0.718162 0.475489
 0.222931 0.582418 ⋅ 0.412739 ⋅ 0.942747
  ⋅ 0.290387 ⋅ 0.876276 0.449718 0.408883

julia> rand(UD(-5, 4), 5, 6)
5×6 Matrix{Float64}:
 -3.24126 -0.896462 -2.59361 0.11748 0.917439 -0.742394
  3.61575 3.95655 -4.05713 -2.69737 -0.846111 -3.27312
 -2.39694 -0.194496 0.946839 -3.9091 2.11152 -4.85219
  2.77711 0.618885 -1.53174 -4.30585 2.2522 1.27031
 -1.65799 -1.4638 -4.91182 -1.24282 2.79811 3.06926

julia> sprand(UD(-5, 4), 5, 6, .7)
ERROR: MethodError: no method matching sprand(::Distributions.Uniform{Float64}, ::Int64, ::Int64, ::Float64)
The function `sprand` exists, but no method is defined for this combination of argument types.

Closest candidates are:
  sprand(::Type{T}, ::Integer, ::Integer, ::AbstractFloat) where T
   @ SparseArrays K:\julia-1.11.4\share\julia\stdlib\v1.11\SparseArrays\src\sparsematrix.jl:2048
  sprand(::Random.AbstractRNG, ::Integer, ::Integer, ::AbstractFloat)
   @ SparseArrays K:\julia-1.11.4\share\julia\stdlib\v1.11\SparseArrays\src\sparsematrix.jl:2042
  sprand(::Random.AbstractRNG, ::Integer, ::Integer, ::AbstractFloat, ::Function, ::Type{T}) where T
   @ SparseArrays K:\julia-1.11.4\share\julia\stdlib\v1.11\SparseArrays\src\sparsematrix.jl:2027
  ...

Stacktrace:
 [1] top-level scope
   @ REPL[6]:1

```

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<div class="post-metadata">

**Author:** ![gdalle](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/gdalle/32/27854_2.png) [@gdalle](https://discourse.julialang.org/u/gdalle)\
**Post date:** [March 22, 2025, 7:56am UTC](https://discourse.julialang.org/t/why-sprand-does-not-accept-a-distribution-arg/127255/2 "2025-03-22T07:56:06Z")

</div>

> [@WalterMadelim](#):
>
> I wonder why this cannot work out

Because Distributions.jl didn’t implement it I guess. And in general you may need two sets of parameters, one for deciding which coefficients are nonzero and one for the distribution of these nonzero coefficients.

> [@WalterMadelim](#):
>
> What is the available method currently then?

I guess you need to initialize a matrix first and then transform only its nonzeros:

```julia
julia> using SparseArrays, Distributions, Random

julia> rng = Xoshiro(1)
Xoshiro(0xfff0241072ddab67, 0xc53bc12f4c3f0b4e, 0x56d451780b2dd4ba, 0x50a4aa153d208dd8, 0x3649a58b3b63d5db)

julia> M = sprand(rng, Bool, 10, 10, 0.5)
10×10 SparseMatrixCSC{Bool, Int64} with 47 stored entries:
 1 ⋅ ⋅ 1 ⋅ ⋅ ⋅ ⋅ 1 1
 1 1 ⋅ 1 1 1 ⋅ ⋅ 1 1
 ⋅ 1 1 ⋅ ⋅ ⋅ 1 1 1 ⋅
 ⋅ 1 ⋅ ⋅ 1 1 1 1 1 ⋅
 ⋅ ⋅ 1 1 1 ⋅ ⋅ ⋅ 1 ⋅
 1 ⋅ ⋅ ⋅ 1 ⋅ ⋅ ⋅ ⋅ ⋅
 ⋅ 1 1 1 1 ⋅ 1 1 1 1
 ⋅ 1 ⋅ 1 ⋅ ⋅ 1 ⋅ ⋅ ⋅
 ⋅ 1 ⋅ 1 1 ⋅ 1 ⋅ 1 ⋅
 1 1 ⋅ ⋅ ⋅ ⋅ ⋅ ⋅ 1 ⋅

julia> N = similar(M, Float64)
10×10 SparseMatrixCSC{Float64, Int64} with 47 stored entries:
 1.00388e218 ⋅ ⋅ 2.7451e-57 ⋅ ⋅ ⋅ ⋅ 2.47e-322 0.0
 6.8074e199 1.38998e218 ⋅ 9.02134e217 1.53991e-71 1.8e-322 ⋅ ⋅ 2.5e-322 2.87e-322
  ⋅ 7.52133e130 2.00183e-23 ⋅ ⋅ ⋅ 1.93e-322 2.27e-322 2.57e-322 ⋅ 
  ⋅ 2.84185e-52 ⋅ ⋅ 3.88592e-109 1.9e-322 2.0e-322 2.3e-322 2.67e-322 ⋅ 
  ⋅ ⋅ 1.42534e-23 7.53433e130 4.86184e-42 ⋅ ⋅ ⋅ 2.7e-322 ⋅ 
 1.44062e-176 ⋅ ⋅ ⋅ 2.36953e-177 ⋅ ⋅ ⋅ ⋅ ⋅ 
  ⋅ 7.55274e130 1.44062e-176 1.44062e-176 2.21129e-312 ⋅ 2.08e-322 2.37e-322 2.8e-322 0.0
  ⋅ 1.44062e-176 ⋅ 2.7451e-57 ⋅ ⋅ 2.1e-322 ⋅ ⋅ ⋅ 
  ⋅ 1.37144e-71 ⋅ 9.02134e217 1.73e-322 ⋅ 2.17e-322 ⋅ 2.9e-322 ⋅ 
 1.44062e-176 1.00838e-176 ⋅ ⋅ ⋅ ⋅ ⋅ ⋅ 2.96e-322 ⋅ 

julia> rand!(rng, Uniform(2, 3), nonzeros(N));

julia> N
10×10 SparseMatrixCSC{Float64, Int64} with 47 stored entries:
 2.62901 ⋅ ⋅ 2.64196 ⋅ ⋅ ⋅ ⋅ 2.3656 2.12425
 2.15288 2.85686 ⋅ 2.1277 2.08739 2.56568 ⋅ ⋅ 2.55904 2.90843
  ⋅ 2.09181 2.169 ⋅ ⋅ ⋅ 2.0948 2.95284 2.56943 ⋅ 
  ⋅ 2.22459 ⋅ ⋅ 2.42544 2.49985 2.74462 2.75591 2.68652 ⋅ 
  ⋅ ⋅ 2.55349 2.84995 2.06013 ⋅ ⋅ ⋅ 2.82558 ⋅ 
 2.57669 ⋅ ⋅ ⋅ 2.76191 ⋅ ⋅ ⋅ ⋅ ⋅ 
  ⋅ 2.83915 2.69511 2.3484 2.27129 ⋅ 2.90834 2.75925 2.60227 2.67956
  ⋅ 2.90274 ⋅ 2.24145 ⋅ ⋅ 2.96495 ⋅ ⋅ ⋅ 
  ⋅ 2.73817 ⋅ 2.17797 2.00311 ⋅ 2.65701 ⋅ 2.17602 ⋅ 
 2.74252 2.19169 ⋅ ⋅ ⋅ ⋅ ⋅ ⋅ 2.53072 ⋅ 

```

---

<div class="post-metadata">

**Author:** ![WalterMadelim](https://avatars.discourse-cdn.com/v4/letter/w/3e96dc/32.png) [@WalterMadelim](https://discourse.julialang.org/u/WalterMadelim)\
**Post date:** [March 22, 2025, 8:07am UTC](https://discourse.julialang.org/t/why-sprand-does-not-accept-a-distribution-arg/127255/3 "2025-03-22T08:07:41Z")

</div>

Thank you very much.  
Your code is a bit advanced for me, maybe I will go with this

```julia
import SparseArrays
import Distributions.Uniform as UDistri
import Distributions.Bernoulli as BDistri
function sp_rand(D, I, J, p)
    Bmat, Mmat = rand(BDistri(p), I, J), rand(D, I, J)
    return SparseArrays.sparse(Mmat .* Bmat)
end

```

> [@gdalle](#):
>
> Because [Distributions.jl](https://juliaregistries.github.io/General/packages/redirect_to_repo/Distributions) didn’t implement it

If this is the case, I’ll suggest them to add this method. Since this is common in research work 🙂

---

<div class="post-metadata">

**Author:** ![gdalle](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/gdalle/32/27854_2.png) [@gdalle](https://discourse.julialang.org/u/gdalle)\
**Post date:** [March 22, 2025, 8:52am UTC](https://discourse.julialang.org/t/why-sprand-does-not-accept-a-distribution-arg/127255/4 "2025-03-22T08:52:28Z")

</div>

> [@WalterMadelim](#):
>
> Your code is a bit advanced for me,

Here it is with some comments:

```julia
# import necessary packages
using SparseArrays, Distributions, Random
# initialize a random number generator with a seed so that
# results are reproducible (not mandatory but good practice)
rng = Xoshiro(1) 
# generate a Boolean "'mask" matrix to decide where the nonzeros are
M = sprand(rng, Bool, 10, 10, 0.5)
# allocate a matrix of the same size and nonzero structure
# but with a floating-point element type
N = similar(M, Float64)
# modify the non-zero coefficients of N in-place
# with the distribution of your choice
UD = Uniform(2, 3)
rand!(rng, UD, nonzeros(N));
# voila!

```

> [@WalterMadelim](#):
>
> maybe I will go with this

You can but it will be much less efficient in high dimension since you generate dense matrices before converting them to sparse format.

> [@WalterMadelim](#):
>
> If this is the case, I’ll suggest them to add this method. Since this is common in research work 🙂

If you want the devs to be aware of that, the best way is to open an issue on the Distributions.jl repo.

---

<div class="post-metadata">

**Author:** ![WalterMadelim](https://avatars.discourse-cdn.com/v4/letter/w/3e96dc/32.png) [@WalterMadelim](https://discourse.julialang.org/u/WalterMadelim)\
**Post date:** [March 22, 2025, 10:38am UTC](https://discourse.julialang.org/t/why-sprand-does-not-accept-a-distribution-arg/127255/5 "2025-03-22T10:38:10Z")

</div>

I’m clearer now. But this is my first time learning about `rand!`, I’m still a bit confused.  
If I want to in-place substitute the second row of a matrix, what should I do?

```julia
julia> b = 9.9 * ones(3, 3)
3×3 Matrix{Float64}:
 9.9 9.9 9.9
 9.9 9.9 9.9
 9.9 9.9 9.9

julia> rand!(b[2, :])
3-element Vector{Float64}:
 0.3852825154281183
 0.7043852897670511
 0.9401658209886775

julia> b # This is unaltered
3×3 Matrix{Float64}:
 9.9 9.9 9.9
 9.9 9.9 9.9
 9.9 9.9 9.9

```

As a comparison, `rand!(b)` works. 🤔

---

<div class="post-metadata">

**Author:** ![abraemer](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/abraemer/32/51403_2.png) [@abraemer](https://discourse.julialang.org/u/abraemer)\
**Post date:** [March 22, 2025, 10:46am UTC](https://discourse.julialang.org/t/why-sprand-does-not-accept-a-distribution-arg/127255/6 "2025-03-22T10:46:19Z")

</div>

> [@WalterMadelim](#):
>
> `b[2, :]`

This creates a copy of the values. You need to use a view instead. Try:

`julia> rand!(view(b, 2, :))`

---

<div class="post-metadata">

**Author:** ![WalterMadelim](https://avatars.discourse-cdn.com/v4/letter/w/3e96dc/32.png) [@WalterMadelim](https://discourse.julialang.org/u/WalterMadelim)\
**Post date:** [March 22, 2025, 11:22am UTC](https://discourse.julialang.org/t/why-sprand-does-not-accept-a-distribution-arg/127255/7 "2025-03-22T11:22:49Z")

</div>

I guess that the `Bool` and `similar` lines can be skipped,  
whereby we end up with this (can we?)

```julia
function sp_rand(Distri, I, J, p)
    M = sprand(I, J, p)
    rand!(Distri, nonzeros(M))
    M
end

```

will the “Bool-precursor” (your version) be faster?

---

<div class="post-metadata">

**Author:** ![WalterMadelim](https://avatars.discourse-cdn.com/v4/letter/w/3e96dc/32.png) [@WalterMadelim](https://discourse.julialang.org/u/WalterMadelim)\
**Post date:** [March 22, 2025, 11:32am UTC](https://discourse.julialang.org/t/why-sprand-does-not-accept-a-distribution-arg/127255/8 "2025-03-22T11:32:55Z")

</div>

For the first time I know the usage of `view` (LOL).  
The functionalities in Julia is something like:  
if you don’t have an opportunity to use it, you’ll never have interests to learn it.

---

<div class="post-metadata">

**Author:** ![stevengj](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/stevengj/32/71_2.png) [@stevengj](https://discourse.julialang.org/u/stevengj)\
**Post date:** [March 22, 2025, 12:10pm UTC](https://discourse.julialang.org/t/why-sprand-does-not-accept-a-distribution-arg/127255/9 "2025-03-22T12:10:24Z")

</div>

> [@WalterMadelim](#):
>
> I wonder why this cannot work out (What is the available method currently then?).

You can use the `rfn` argument of `sprand` for this:

```julia
julia> using Distributions, SparseArrays

julia> sprand(5,6,0.7, n -> rand(Uniform(-5,4),n))
5×6 SparseMatrixCSC{Float64, Int64} with 22 stored entries:
 -0.0667353 -0.758496 2.84818 ⋅ -0.0465101 -3.6376
   ⋅ ⋅ 0.42936 2.03778 1.16782 ⋅ 
  0.732217 1.00664 -3.02505 2.40859 -4.59048 2.14958
   ⋅ 2.42693 1.88046 ⋅ 2.13845 ⋅ 
  2.06068 -4.15294 -3.18514 ⋅ -3.74181 -4.91287

```

Distributions.jl could make this easier by adding a method:

```julia
SparseArrays.sprand(dist::Sampleable, m::Integer, n::Integer, density::AbstractFloat) = sprand(m, n, density, n -> rand(dist, n))

```

I see that you already opened an issue ([May I suggest adding the sprand(::Distributions.Distribution, ...) method, like rand() does? · Issue #1955 · JuliaStats/Distributions.jl · GitHub](https://github.com/JuliaStats/Distributions.jl/issues/1955))

---

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**Author:** ![gdalle](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/gdalle/32/27854_2.png) [@gdalle](https://discourse.julialang.org/u/gdalle)\
**Post date:** [March 23, 2025, 8:31am UTC](https://discourse.julialang.org/t/why-sprand-does-not-accept-a-distribution-arg/127255/10 "2025-03-23T08:31:58Z")

</div>

> [@WalterMadelim](#):
>
> I guess that the `Bool` and `similar` lines can be skipped,

Yeah they might be superfluous indeed, I just wanted to show the conceptual difference between deciding the sparsity pattern (which can be done with `Bool` values) and drawing the actual coefficients.  
I also didn’t know about `rfn`, which sounds like the right solution.

---

<div class="post-metadata">

**Author:** ![WalterMadelim](https://avatars.discourse-cdn.com/v4/letter/w/3e96dc/32.png) [@WalterMadelim](https://discourse.julialang.org/u/WalterMadelim)\
**Post date:** [April 3, 2025, 4:02am UTC](https://discourse.julialang.org/t/why-sprand-does-not-accept-a-distribution-arg/127255/11 "2025-04-03T04:02:18Z")

</div>

Maybe this need is not that strong. See [this](https://github.com/JuliaStats/Distributions.jl/issues/1955#issuecomment-2774435390).