# How can I solve "no method matching Chains" in Turing - Julia
**URL:** https://discourse.julialang.org/t/how-can-i-solve-no-method-matching-chains-in-turing-julia/27166
**Category:** Probabilistic Programming
**Tags:** turing
**Created:** [August 5, 2019, 6:34am UTC](https://discourse.julialang.org/t/how-can-i-solve-no-method-matching-chains-in-turing-julia/27166 "2019-08-05T06:34:07Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@Manu\_Francis](https://discourse.julialang.org/u/Manu_Francis)
#### Post date: [August 5, 2019, 6:34am UTC](https://discourse.julialang.org/t/how-can-i-solve-no-method-matching-chains-in-turing-julia/27166/1 "2019-08-05T06:34:07Z")
Hi,
I am trying to learn as a beginner of Julia and Turing and run the following program given in Turing tutorial.
```julia
# Import libraries.
using Turing, StatsPlots, Random
# Set the true probability of heads in a coin.
p_true = 0.5
# Iterate from having seen 0 observations to 100 observations.
Ns = 0:100;
# Draw data from a Bernoulli distribution, i.e. draw heads or tails.
Random.seed!(12)
data = rand(Bernoulli(p_true), last(Ns))
# Declare our Turing model.
@model coinflip(y) = begin
# Our prior belief about the probability of heads in a coin.
p ~ Beta(1, 1)
# The number of observations.
N = length(y)
for n in 1:N
# Heads or tails of a coin are drawn from a Bernoulli distribution.
y[n] ~ Bernoulli(p)
end
end;
# Settings of the Hamiltonian Monte Carlo (HMC) sampler.
iterations = 1000
ϵ = 0.05
τ = 10
# Start sampling.
chain = sample(coinflip(data), HMC(iterations, ϵ, τ));
# Construct summary of the sampling process for the parameter p, i.e. the probability of heads in a coin.
psummary = Chains(chain[:p])
histogram(psummary)
```
[https://turing.ml/docs/using-turing/quick-start](http://Reference)
While running, I am getting the following error as follows:
```julia
MethodError: no method matching Chains(::Chains{Union{Missing, Float64},Float64,NamedTuple{(:parameters,),Tuple{Array{String,1}}},NamedTuple{(:samples, :hashedsummary),Tuple{Array{Turing.Utilities.Sample,1},Base.RefValue{Tuple{UInt64,Array{ChainDataFrame,1}}}}}})
Closest candidates are:
Chains(::Chains{A,T,K,L}, !Matched::Any; sorted) where {A, T, K, L} at C:\Users\z5168736\.julia\packages\MCMCChains\x3N5v\src\chains.jl:144
Chains(!Matched::AxisArrays.AxisArray{A,3,D,Ax} where Ax where D, !Matched::T, !Matched::K<:NamedTuple, !Matched::L<:NamedTuple) where {A, T, K<:NamedTuple, L<:NamedTuple} at C:\Users\z5168736\.julia\packages\MCMCChains\x3N5v\src\MCMCChains.jl:50
Chains(!Matched::Array{Array{A<:Union{Missing, Real},1},1}) where A<:Union{Missing, Real} at C:\Users\z5168736\.julia\packages\MCMCChains\x3N5v\src\chains.jl:27
...
top-level scope at none:0
```
How can I solve this error?
Thanks in Advance !
Manu
---
### Author:  [@trappmartin](https://discourse.julialang.org/u/trappmartin)
#### Post date: [August 5, 2019, 8:38am UTC](https://discourse.julialang.org/t/how-can-i-solve-no-method-matching-chains-in-turing-julia/27166/2 "2019-08-05T08:38:43Z")
The `sample` function already returns a `Chains` object. Meaning, you do not have to construct one explicitly.
Removing this line:
```julia
psummary = Chains(chain[:p])
```
Should solve the issue. The description in the tutorial has not been updated, we are a bit behind with updating the docs at the moment. But I will open a PR that fixes the explanation.
---
### Author:  [@mohamed82008](https://discourse.julialang.org/u/mohamed82008)
#### Post date: [August 5, 2019, 9:45am UTC](https://discourse.julialang.org/t/how-can-i-solve-no-method-matching-chains-in-turing-julia/27166/3 "2019-08-05T09:45:55Z")
You can do `histogram(chain)` or `histogram(chain[:p])`. `chain[:p]` is also an instance of `Chains`.
---
### Author:  [@Manu\_Francis](https://discourse.julialang.org/u/Manu_Francis)
#### Post date: [August 6, 2019, 1:26am UTC](https://discourse.julialang.org/t/how-can-i-solve-no-method-matching-chains-in-turing-julia/27166/4 "2019-08-06T01:26:49Z")
@mohamed82008: Thanks a lot for your reply !!
---
### Author:  [@Manu\_Francis](https://discourse.julialang.org/u/Manu_Francis)
#### Post date: [August 6, 2019, 1:27am UTC](https://discourse.julialang.org/t/how-can-i-solve-no-method-matching-chains-in-turing-julia/27166/5 "2019-08-06T01:27:03Z")
@trappmartin: Thank you !!