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Makie.jl plots

This page shows an example of plotting MCMCChains.jl with Makie.jl. The example is meant to provide an useful basis to build upon. Let's define some random chain and load the required packages:

using MCMCChains

chns = Chains(randn(300, 5, 3), [:A, :B, :C, :D, :E])
Chains MCMC chain (300×5×3 Array{Float64, 3}):

Iterations        = 1:1:300
Number of chains  = 3
Samples per chain = 300
parameters        = A, B, C, D, E

Summary Statistics
  parameters      mean       std      mcse    ess_bulk   ess_tail      rhat    ⋯
      Symbol   Float64   Float64   Float64     Float64    Float64   Float64    ⋯

           A    0.0324    1.0226    0.0340    903.2697   869.7326    1.0016    ⋯
           B    0.0083    0.9727    0.0337    830.5137   877.8688    1.0015    ⋯
           C    0.0038    1.0124    0.0343    867.8475   848.6913    0.9999    ⋯
           D   -0.0481    0.9906    0.0327    918.1466   839.6162    1.0011    ⋯
           E    0.0060    0.9734    0.0302   1038.5941   912.3222    1.0003    ⋯
                                                                1 column omitted

Quantiles
  parameters      2.5%     25.0%     50.0%     75.0%     97.5%
      Symbol   Float64   Float64   Float64   Float64   Float64

           A   -2.0496   -0.6946    0.0758    0.7028    2.1171
           B   -1.8296   -0.6719    0.0039    0.6825    1.9137
           C   -1.9518   -0.6502   -0.0133    0.6851    1.9428
           D   -2.0363   -0.6882   -0.0158    0.6090    1.8324
           E   -1.8552   -0.6468    0.0328    0.6693    1.8702

A basic way to visualize the chains is to show the drawn samples at each iteration. Colors depict different chains.

using CairoMakie
CairoMakie.activate!(; type="svg")

params = names(chns, :parameters)

n_chains = length(chains(chns))
n_samples = length(chns)

fig = Figure(; resolution=(1_000, 800))

for (i, param) in enumerate(params)
    ax = Axis(fig[i, 1]; ylabel=string(param))
    for chain in 1:n_chains
        values = chns[:, param, chain]
        lines!(ax, 1:n_samples, values; label=string(chain))
    end

    hideydecorations!(ax; label=false)
    if i < length(params)
        hidexdecorations!(ax; grid=false)
    else
        ax.xlabel = "Iteration"
    end
end

fig
Example block output

Next, we can add a second row of plots next to it which show the density estimate for these samples:

for (i, param) in enumerate(params)
    ax = Axis(fig[i, 2]; ylabel=string(param))
    for chain in 1:n_chains
        values = chns[:, param, chain]
        density!(ax, values; label=string(chain))
    end

    hideydecorations!(ax)
    if i < length(params)
        hidexdecorations!(ax; grid=false)
    else
        ax.xlabel = "Parameter estimate"
    end
end

axes = [only(contents(fig[i, 2])) for i in 1:length(params)]
linkxaxes!(axes...)

fig
Example block output

Finally, let's add a simple legend. Thanks to setting label above, this legend will have the right labels:

axislegend(first(axes))

fig
Example block output