# Unique (indices) method similar to MATLAB

**URL:** https://discourse.julialang.org/t/unique-indices-method-similar-to-matlab/34446
**Category:** General Usage
**Tags:** question
**Created:** [February 11, 2020, 12:35am UTC](https://discourse.julialang.org/t/unique-indices-method-similar-to-matlab/34446 "2020-02-11T00:35:27Z")
**Posts on this page:** 1
**Showing post:** 6

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### Author: ![mcabbott](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/mcabbott/32/6603_2.png) [@mcabbott](https://discourse.julialang.org/u/mcabbott)
#### Post date: [February 11, 2020, 10:18am UTC](https://discourse.julialang.org/t/unique-indices-method-similar-to-matlab/34446/6 "2020-02-11T10:18:28Z")

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For completeness, perhaps this thread should mention [GroupSlices.jl](https://github.com/mcabbott/GroupSlices.jl) (not written by me!) which in fact doesn’t return Matlab’s 3rd output:

```julia
A = [9, 2, 9, 5];
C = unique(A)
ia = unique(i -> A[i], 1:length(A)) # [1, 2, 4]
A[ia] == C
using GroupSlices
ig = groupslices(A) # [1, 2, 1, 4]
A[ig] == A # not matlab's ic
ia == firstinds(ig)

```

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