You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: ipctb_spm_clusters.m
    path of file: ./repos/bspm/thirdparty/MIALAB/gipc1d/ipctb_spm5_files
    
    the code of the file until where you have to start completion: function A = ipctb_spm_clusters(L)

    
function A = ipctb_spm_clusters(L)
% Returns the cluster index for a point list
% FORMAT [A] = spm_clusters(L)
% L     - locations [x y x]' {in voxels}
%
% A     - cluster index or region number
%_______________________________________________________________________
%
% spm_clusters characterizes a point list of voxel values defined with
% their locations (L) in terms of edge, face and vertex connected
% subsets, returning a list of indices in A, such that the ith location
% belongs to cluster A(i) (using an 18 connectivity scheme).
%
% The programming interface of this routine is modeled on the "old"
% spm_clusters to avoid the need to recode any other parts. The "old"
% version had the unfourtunate tend