Julia and dbscan clustering: how extract elements from resulting structure? - indexing

Question

Warning: this is from a julia n00b!
After performing dbscan on a point coordinate array in Julia. (Note that this is not the 'distance based method' that returns 'assignments' as part of the result structure, but the 'adjacency list' method). Documentation here. I attempt to access the vector containing the indices, but I am at a loss when trying to retrieve the members of individual clusters:
dbr = dbscan(pointcoordinates, .1, min_neighbors = 10, min_cluster_size = 10)
13-element Array{DbscanCluster,1}:
DbscanCluster(17, [4, 12, 84, 90, 94, 675, 676, 737, 873, 965], [27, 108, 177, 880, 954, 1050, 1067])
DbscanCluster(10, Int64[], [46, 48, 51, 57, 188, 225, 226, 228, 270, 542])
DbscanCluster(11, [48, 51, 228], [46, 49, 57, 188, 225, 226, 270, 542])
DbscanCluster(14, [418, 759, 832, 988, 1046], [830, 831, 855, 865, 989, 991, 996, 1021, 1070])
DbscanCluster(10, Int64[], [624, 654, 664, 803, 805, 821, 859, 987, 1057, 1069])
It is easy to retrieve a single cluster from the array:
> dbr[1]
DbscanCluster(17, [4, 12, 84, 90, 94, 675, 676, 737, 873, 965], [27, 108, 177, 880, 954, 1050, 1067])
But how do i get the stuff inside DBscanCluster?
a = dbr[1]
DbscanCluster(17, [4, 12, 84, 90, 94, 675, 676, 737, 873, 965], [27, 108, 177, 880, 954, 1050, 1067])
In [258]:
a[1]
MethodError: no method matching getindex(::DbscanCluster, ::Int64)
Thank you for your help, and sorry if I am missing something glaring!

Answer 1

What makes you say that DbscanCluster is a child of array?
julia> DbscanCluster <: AbstractArray
false
You might be confused by Array{DbscanCluster,1} in your result, but this just tells you that the object returned by the dbscan call is an Array the elements of which are of type DbscanCluster - this does not tell you anything about whether those elements themselves are subtypes of Array.
As for how to get the indexes, the docs for DbscanResult show that the type has three fields:
seeds::Vector{Int}: indices of cluster starting points
assignments::Vector{Int}: vector of clusters indices, where each point was assigned to
counts::Vector{Int}: cluster sizes (number of assigned points)
each of which you can access with dot notation by doing e.g. drb[1].assignments.
If you want to get say the counts for all the 13 clusters in your results, you can broadcast getproperty like so:
getproperty.(drb, :counts)
Note that counts does not exist for in the case of the "adjacency lists" method of dbscan, one can use:
getproperty.(drb, :core_indices)