The function groupslices is related to unique, but instead of returning the unique elements,
it returns a list of indices showing where an equivalent entry first appeared. Like this:
(v1.2) pkg> add GroupSlices
julia> using GroupSlices
julia> V = rand('α':'γ', 5)
5-element Array{Char,1}:
'β'
'β'
'γ'
'α'
'β'
julia> groupslices(V)
5-element Array{Int64,1}:
1
1
3
4
1
julia> unique(V)
3-element Array{Char,1}:
'β'
'γ'
'α'
julia> M = rand(2:4, 2,13)
2×13 Array{Int64,2}:
2 2 3 3 3 4 2 2 2 4 3 2 4
4 4 4 4 4 4 3 4 3 2 3 4 2
julia> groupslices(M, dims=2) |> transpose
1×13 LinearAlgebra.Transpose{Int64,Array{Int64,1}}:
1 1 3 3 3 6 7 1 7 10 11 1 10
julia> unique(M, dims=2)
2×6 Array{Int64,2}:
2 3 4 2 4 3
4 4 4 3 2 3This package was written by AndyGreenwell in 2015, originally for Julia PRs #14142 and #15503.
My fork is now the registered version. It has minimal changes to make it work on Julia 1.0,
and to accept keywords like dims=2 (although groupslices(M,2) will also still work).
See JuliaLang/julia#1845 for discussion of possible replacements.