# Sampling Multiple samples from NormalInverseGamma distribution

**URL:** <https://discourse.julialang.org/t/sampling-multiple-samples-from-normalinversegamma-distribution/10575>\
**Category:** Statistics\
**Created:** [April 27, 2018, 12:08pm UTC](https://discourse.julialang.org/t/sampling-multiple-samples-from-normalinversegamma-distribution/10575 "2018-04-27T12:08:23Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![v-i-s-h](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/v-i-s-h/32/46152_2.png) [@v-i-s-h](https://discourse.julialang.org/u/v-i-s-h)\
**Post date:** [April 27, 2018, 12:08pm UTC](https://discourse.julialang.org/t/sampling-multiple-samples-from-normalinversegamma-distribution/10575/1 "2018-04-27T12:08:23Z")

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Hi,

I’m trying to sample multiple samples from a `NormalInversaGamma` distribution. I was using `rand()` function with two arguments, but is getting the following error:

```julia
julia> using ConjugatePriors
julia> D = ConjugatePriors.NormalInverseGamma( 0.00, 1.0/0.01, 1.0, 1.0 )
ConjugatePriors.NormalInverseGamma{Float64}(mu=0.0, v0=100.0, shape=1.0, scale=1.0)

julia> rand( D, 4 )
ERROR: MethodError: Cannot `convert` an object of type Tuple{Float64,Float64} to an object of type Float64
This may have arisen from a call to the constructor Float64(...),
since type constructors fall back to convert methods.
Stacktrace:
 [1] _rand!(::ConjugatePriors.NormalInverseGamma{Float64}, ::Array{Float64,1}) at /home/vish/.julia/v0.6/Distributions/src/genericrand.jl:37
 [2] rand(::ConjugatePriors.NormalInverseGamma{Float64}, ::Int64) at /home/vish/.julia/v0.6/Distributions/src/univariates.jl:182

```

I think the problem is because NIG gives a sample vector (tuple actually), `rand()` is getting confused to convert it to a Float64 entry. Why cannot `rand()` return a vector of tuples in this case?

With Regards,  
Vishnu Raj

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<div class="post-metadata">

**Author:** ![Tamas\_Papp](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/tamas_papp/32/25949_2.png) [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)\
**Post date:** [April 27, 2018, 12:37pm UTC](https://discourse.julialang.org/t/sampling-multiple-samples-from-normalinversegamma-distribution/10575/2 "2018-04-27T12:37:29Z")

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This seems to be a known issue:  
[https://github.com/JuliaStats/ConjugatePriors.jl/issues/19](https://github.com/JuliaStats/ConjugatePriors.jl/issues/19)  
If the package is maintained, perhaps a trivial PR would help?

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**Author:** ![mschauer](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/mschauer/32/13946_2.png) [@mschauer](https://discourse.julialang.org/u/mschauer)\
**Post date:** [April 27, 2018, 4:26pm UTC](https://discourse.julialang.org/t/sampling-multiple-samples-from-normalinversegamma-distribution/10575/3 "2018-04-27T16:26:25Z")

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Distributions has much better support for other types than Int, Float64 and Vector{Float64} by now, maybe it is really not so difficult. A PR would be very welcome.