This package provides memory efficient one-hot array encodings. It was originally part of Flux.jl.
julia> using OneHotArrays
julia> m = onehotbatch([10, 20, 30, 10, 10], 10:10:40)
4×5 OneHotMatrix(::Vector{UInt32}) with eltype Bool:
1 ⋅ ⋅ 1 1
⋅ 1 ⋅ ⋅ ⋅
⋅ ⋅ 1 ⋅ ⋅
⋅ ⋅ ⋅ ⋅ ⋅
julia> dump(m)
OneHotMatrix{UInt32, Vector{UInt32}}
indices: Array{UInt32}((5,)) UInt32[0x00000001, 0x00000002, 0x00000003, 0x00000001, 0x00000001]
nlabels: Int64 4
julia> @which rand(100, 4) * m
*(A::AbstractMatrix, B::Union{OneHotArray{var"#s29", 1, var"N+1", I}, Base.ReshapedArray{Bool, var"N+1", <:OneHotArray{var"#s29", <:Any, <:Any, I}}} where {var"#s29", var"N+1", I})
@ OneHotArrays ~/.julia/packages/OneHotArrays/DqU9m/src/linalg.jl:7