Remove consecutive duplicates in Julia

Question

I am quite new in Julia and I don't know how to remove consecutive duplicates in an array. For example if you take this array :

   `v=[8,8,8,9,5,5,8,8,1];`

I would like to obtain the vector v1 such that:

v1 = [8,9,5,8,1];

Could anyone help me? Many thanks.

Answer 1

One method could be to define:

function fastuniq(v)
  v1 = Vector{eltype(v)}()
  if length(v)>0
    laste = v[1]
    push!(v1,laste)
    for e in v
      if e != laste
        laste = e
        push!(v1,laste)
      end
    end
  end
  return v1
end

And with this function, you have:

julia> println(fastuniq(v))
[8,9,5,8,1]

But, when dealing with arrays, one need to decide if elements are to be deep or shallow copied. In case of integers, it doesn't matter.

Answer 2

In StatsBase.jl there is an rle function (Run-length encoding) that does exactly this.

Answer 3

This is a lot slower than @DanGetz's function but here is a way to do it in one line:

function notsofastunique(v)
  return [v[1]; v[2:end][v[2:end] .!= v[1:end-1]]]
end


>println(notsofastunique(v))
[8,9,5,8,1]

Maybe it's useful for someone looking for a vecotrised solution.