# Find neighbored segments/labels in Matrix

**URL:** <https://discourse.julialang.org/t/find-neighbored-segments-labels-in-matrix/64151>\
**Category:** General Usage\
**Tags:** images, array\
**Created:** [July 6, 2021, 2:42pm UTC](https://discourse.julialang.org/t/find-neighbored-segments-labels-in-matrix/64151 "2021-07-06T14:42:15Z")\
**Posts on this page:** 1\
**Showing post:** 8

<div class="post-metadata">

**Author:** ![sijo](https://avatars.discourse-cdn.com/v4/letter/s/da6949/32.png) [@sijo](https://discourse.julialang.org/u/sijo)\
**Post date:** [July 6, 2021, 6:18pm UTC](https://discourse.julialang.org/t/find-neighbored-segments-labels-in-matrix/64151/8 "2021-07-06T18:18:18Z")

</div>

By the way, with just one line changed the function will work for arrays of any dimension:

```julia
julia> function find_neighbors(A; nsegments=maximum(A))
           # These two should be compared to see which one performs better:
           flags = zeros(Bool, nsegments, nsegments)
           #flags = falses(nsegments, nsegments) # Uses a BitArray instead of an array of Bool
           
           indices = CartesianIndices(A)
           neighbors = -oneunit(indices[1]):oneunit(indices[1]) # ← this line changed
           for I in indices
               for N in neighbors
                   if I+N in indices
                       flags[A[I+N], A[I]] = true
                   end
               end
           end

           # Unset diagonal elements since a segment is not neighbor of itself
           flags[diagind(flags)] .= false

           return Dict(seg => findall(col) for (seg, col) in enumerate(eachcol(flags)))
       end
find_neighbors (generic function with 1 method)

julia> A = [1 2 3
            1 1 3
            4 4 4;;;
            
            1 2 3
            1 3 3
            1 5 5]
3×3×2 Array{Int64, 3}:
[:, :, 1] =
 1 2 3
 1 1 3
 4 4 4

[:, :, 2] =
 1 2 3
 1 3 3
 1 5 5

julia> find_neighbors(A)
Dict{Int64, Vector{Int64}} with 5 entries:
  5 => [1, 3, 4]
  4 => [1, 3, 5]
  2 => [1, 3]
  3 => [1, 2, 4, 5]
  1 => [2, 3, 4, 5]

```

Isn’t this cool? (yeah I know it’s just a rehash of [that one](https://discourse.julialang.org/t/seven-lines-of-julia-examples-sought/50416/48) 🙂 )

---

_[View the full topic](https://discourse.julialang.org/t/find-neighbored-segments-labels-in-matrix/64151)._