Makie Categorical colors

General Usage
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1

How to map a categorical column to a categorical color palette in Makie?

using CairoMakie,AlgebraOfGraphics,RDatasets
diamonds = dataset("ggplot2","diamonds")

In AoG it’s just

data(diamonds) * mapping(:Carat, :Price; color=:Color) * visual(Scatter) |> draw

image
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but how to do it in Makie?

julia> scatter(diamonds.Carat, diamonds.Price; color=string.(diamonds.Color))
ERROR: Unknown color: E
2

I thought “surely Categorical should work”, but surprisingly it doesn’t:

julia> scatter(rand(100), rand(100), color=Categorical(rand("abc", 100)))
ERROR: MethodError: no method matching to_color(::Categorical)

Probably a bug, as this

scatter(Categorical(rand("abc", 100)))

works.

1 Like
3

If I pass color= strings it tries to parse them as color names and passing CategoricalArrays.CategoricalVector fails, but passing numbers makes a plot.

That doesn’t seem like an ideal API in the sense that color names are very different from values to be mapped into colors so I wouldn’t expect them to be accepted by the same kwarg.

julia> scatter(
    diamonds.Carat, 
    diamonds.Price; 
    color=levelcode.(diamonds.Cut), 
    colormap=Makie.wong_colors(),
)

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Though is it me or is there too much yellow there, maybe it’s somehow treating it as continuous rather than categorical?

4

A workaround (or maybe the official solution?) is to set the label keyword to your category/string instead of the color keyword and use a loop.

EDIT: I misread the question/thread at first, sorry.

5

A vector of colors passed to colormap is always interpreted as continuous. We probably need an overload to get Categorical inputs to color to just work…

2 Likes
6

The Makie has its own elegant methods only with the help of groupby() function from DataFrames, the following code works:

using CairoMakie, RDatasets, DataFrames
diamonds = dataset(“ggplot2”,“diamonds”)
fig = Figure()
ax = Axis(fig[1,1])
for i in groupby(diamonds, :color)
scatter!(ax, i.carat, i.price, label=unique(i.color))
end
fig[1,2] = Legend(fig, ax, “Color”)