"Wrong" order from names(chain, :parameters)

[knuesel]

Consider this example:

@model function mymodel(x)
    σ ~ LogNormal()
    a ~ Normal()
    c ~ Normal()
    b ~ Normal()
    x .~ Normal(a+b+c, σ)
end

model = mymodel(randn(1000))
ch = sample(model, NUTS(0.65), 100)
plot(ch)

This plots the parameters in the order σ, a, c, b. This matches the order of parameters in the underlying AxisArray. However, retrieving the parameter list with names gives a different order:

julia> names(ch, :parameters)
4-element Vector{Symbol}:
 :a
 :b
 :σ
 :c

My use case: I want to add things on the plots created by plot(ch). To modify the plot for the ith parameter I can do plot!(..., subplot=2i). But I can't find a good way to get the list of parameters in the right order...

[cpfiffer]

Part of this is because names is intended to be used to get out parameters that fall in different sections, so it adds things in a weird order:

MCMCChains.jl/src/chains.jl

Lines 520 to 526 in b1e4c0e

	function Base.names(c::Chains, sections)
	names = Symbol[]
	for section in sections
	append!(names, c.name_map[section])
	end
	return names
	end

Could this work for you?

chain.value.axes[2].val

[knuesel]

But I'm getting the names from one specific section (:parameters) :

MCMCChains.jl/src/chains.jl

Line 513 in b1e4c0e

Base.names(chains::Chains, section::Symbol) = convert(Vector{Symbol}, chains.name_map[section])

so it's not clear why the order would be wrong?

Thanks for the suggestion! I think it's equivalent to names(chain) ? It returns the right order, but with lots of other values. So the following workaround seems to work:

params = names(ch)[1:length(names(ch, :parameters))]

[devmotion]

The MWE is fixed by #332. With the PR one gets

julia> names(ch, :parameters)
4-element Vector{Symbol}:
 :σ
 :a
 :c
 :b