How to unstack multiple columns with Julia DataFrames.

MultipleUnstack.jl

### A Pluto.jl notebook ###
# v0.11.9

using Markdown
using InteractiveUtils

# ╔═╡ d10371f6-e94c-11ea-0309-5788d6e340b3
begin
	using Pkg
	Pkg.activate(".")
	using DataFrames, Underscores
end

# ╔═╡ eaa10ed8-ea13-11ea-32c5-67b6ea3189ba
example_df = DataFrame(:Run=>[1, 1, 2, 2, 3, 3],
	                   :Type=>["a", "b", "a", "b", "a", "b"],
	                   :x1=>[0.1, 0.2, 0.3, 0.4, 0.5, 0.6],
	                   :x2=>[0.6, 0.5, 0.4, 0.3, 0.2, 0.1])

# ╔═╡ 7e15e0f0-e988-11ea-06bf-1547cbce413f
desired_df = DataFrame(:Run=>[1, 2, 3],
	                   :a_x1=>[0.1, 0.3, 0.5],
	                   :b_x1=>[0.2, 0.4, 0.6],
		               :a_x2=>[0.6, 0.4, 0.2],
	                   :b_x2=>[0.5, 0.3, 0.1])

# ╔═╡ 19fabe14-e966-11ea-29bf-bf4757345e6b
@_ example_df |>
   groupby(__, :Run) |>
   combine(__, [("Type", v) => ((x, y) -> y[x .== t]) => t*"_"*v for v in ["x1", "x2"]                 for t in unique(example_df.Type)])

# ╔═╡ bd6ff950-e98a-11ea-1d03-576ddfb22d12
@_ example_df |>
   [unstack(__, :Run, :Type, v, renamecols = x->x*"_"*v) for v in ["x1", "x2"]] |>
   outerjoin(__..., on=:Run)

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