`corner` plot issue

[yebai]

The following example errors. It seems the issue is from upper stream packages instead of MCMCChains.

Note that the corner plot works fine when the number of variables is smaller than 3.

julia> val = rand(500, 4, 3);

julia> chn = Chains(val, [:a, :b, :c, :d]);

julia> corner(chn)


ERROR: The sum of widths must be 1!
Stacktrace:
  [1] error(s::String)
    @ Base ./error.jl:35
  [2] Plots.GridLayout(::Int64, ::Vararg{…}; parent::Plots.RootLayout, widths::Vector{…}, heights::Vector{…}, kw::@Kwargs{})
    @ Plots ~/.julia/packages/Plots/ju9dp/src/layouts.jl:232
  [3] grid(::Int64, ::Vararg{Int64}; kw::@Kwargs{widths::Vector{Float64}, heights::Vector{Float64}})
    @ Plots ~/.julia/packages/Plots/ju9dp/src/layouts.jl:209
  [4] macro expansion
    @ ~/.julia/packages/StatsPlots/cStOe/src/cornerplot.jl:29 [inlined]
  [5] apply_recipe(plotattributes::AbstractDict{Symbol, Any}, cp::StatsPlots.CornerPlot)
    @ StatsPlots ~/.julia/packages/RecipesBase/BRe07/src/RecipesBase.jl:300
  [6] _process_userrecipes!(plt::Any, plotattributes::Any, args::Any)
    @ RecipesPipeline ~/.julia/packages/RecipesPipeline/BGM3l/src/user_recipe.jl:38
  [7] recipe_pipeline!(plt::Any, plotattributes::Any, args::Any)
    @ RecipesPipeline ~/.julia/packages/RecipesPipeline/BGM3l/src/RecipesPipeline.jl:72
  [8] _plot!(plt::Plots.Plot, plotattributes::Any, args::Any)
    @ Plots ~/.julia/packages/Plots/ju9dp/src/plot.jl:223
  [9] #plot#188
    @ ~/.julia/packages/Plots/ju9dp/src/plot.jl:102 [inlined]
 [10] plot
    @ ~/.julia/packages/Plots/ju9dp/src/plot.jl:93 [inlined]
 [11] corner(args::Chains{Float64, AxisArrays.AxisArray{…}, Missing, @NamedTuple{…}, @NamedTuple{}})
    @ MCMCChains ~/.julia/packages/RecipesBase/BRe07/src/RecipesBase.jl:427
 [12] top-level scope
    @ REPL[53]:1
Some type information was truncated. Use `show(err)` to see complete types.

[penelopeysm]

I looked into this, and it's a classic problem. Plots.jl checks that the widths add up to 1 using:

        if sum(widths) != 1
            error("The sum of widths must be 1!")
        end

With the example in the docs

using MCMCChains
using StatsPlots

# Define the experiment
n_iter = 100
n_name = 3
n_chain = 2

# experiment results
val = randn(n_iter, n_name, n_chain) .+ [1, 2, 3]'
val = hcat(val, rand(1:2, n_iter, 1, n_chain))

# construct a Chains object
chn = Chains(val, [:A, :B, :C, :D])

corner(chn)

it turns out that

widths = [0.3, 0.3, 0.3, 0.1]

and ...

julia> 0.3 + 0.3 + 0.3 + 0.1
0.9999999999999999

[penelopeysm]

Upstream PR: JuliaPlots/Plots.jl#4972

[penelopeysm]

Merged now, will be fixed with the next release of Plots.jl