Custom statistics

[Mattriks]

Does Gadfly support custom statistics?

[Mattriks]

Yes!:

# This uses davidavdav/CHull.jl
using DataFrames, CHull

type ChullStatistic <: Gadfly.StatisticElement
end

function Gadfly.input_aesthetics(stat::ChullStatistic)
    return [:x, :y]
end

function Gadfly.output_aesthetics(stat::ChullStatistic)
    return [:x, :y]
end

function Gadfly.default_scales(stat::ChullStatistic)
    return [Gadfly.Scale.x_continuous(), Gadfly.Scale.y_continuous()]
end


function Gadfly.Stat.apply_statistic(stat::ChullStatistic,
                         scales::Dict{Symbol, Gadfly.ScaleElement},
                         coord::Gadfly.CoordinateElement,
                         aes::Gadfly.Aesthetics)
    xy = hcat(aes.x, aes.y)
    p = chull(xy)
    hull = p.points[p.vertices,:]
    hull = vcat(hull, hull[1,:]')

    aes.x = hull[:,1]
    aes.y = hull[:,2]
end


Stat_chull = ChullStatistic

D = DataFrame(x=randn(50), y=randn(50))
layer1 = layer(Geom.point)
layer2 = layer(Stat_chull, Geom.path)
p = plot(D, x=:x, y=:y, layer1, layer2)

[Mattriks]

I think it would be good to add a page to the Gadfly documentation titled "Custom statistics and custom geometries", which includes examples as above.

[tlnagy]

That sounds like a fantastic idea. The only thing I don't like about the given example is that it has another dependency. I don't have to time to create the example myself, but if you want to go for it, I'll gladly review it and merge it.

[tlnagy]

Do you think it would be possible to update this to not use an outside dependency? I don't want the Gadfly docs to get too hard to build, that's the only reason.

I think it would be great to have this in the docs. If you need help with the new style of docs, Documenter.jl has some pretty decent examples: https://juliadocs.github.io/Documenter.jl/latest/