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: mask2clusters.m
    path of file: ./repos/CanlabCore/CanlabCore/Cluster_contig_region_tools
    
    the code of the file until where you have to start completion: function [clusters,CLU,subclusters] = mask2clusters(P,varargin)
% Extracts clusters and con img data from mask
%

    
function [clusters,CLU,subclusters] = mask2clusters(P,varargin)
% Extracts clusters and con img data from mask
%
% Use with *mask_intersection.m*
%
% To get clusters but not extract data, enter only one argument.
%
% To get clusters and choose extraction imgs with the GUI, enter an empty [] 2nd argument.
%
% :Usage:
% ::
%
%    [clusters,CLU,subclusters] = mask2clusters(img mask file with voxels,[imgs to extract data from],[df])
%
%
% DOES *NOT* CONVERT BETWEEN DIFFERENT VOXEL SIZES AND POSITIONS BETWEEN IMNAMES AND SPM/VOL STRUCTS
%
% :See also: roi_probe
%
% If no imgs are entered, Z-scores are values from mask
%
% If df is entered, values in mask img are converted to Z-scores with spm_t2z.m
%
% If extract img names are empty and df is entered, assume we're using
% values from mask as t-values and convert to Z-scores
%
% WARNING: for spm2 compatibility, ABSOLUTE VALUES of voxel sizes are
% returned; e.g., ignores analyze flipping in SPM2.
%
% % Matlab 6.5/OSX bug gives seg fault or something if mask is too big.
%
% :Example:
% ::
%
%    cl = mask2clusters('myimage.img',[img string mtx],[]); % no z-score
%    conversion, extracts data from [img string mtx]
%
%    cl = mask2clusters('rob_tmap_0002_filt_t_3-05_k10_neg.img')
%
%    % This one works with already-loaded image data and a mat matrix:
%    V = spm_vol('rob_tmap_0002_filt_t_3-05_k10_neg.img'); dat = spm_read_vols(V);
%    cl = mask2clusters(dat,V.mat);
%
%
% ..
%    tor wager
%
%    modification 2/27/03
% ..

% ..
%    set up inputs
% ..
clusters = [];
df = []; imP = [];  resl = 0; vmat = [];


for i = 1:length(varargin)
    tmp = varargin{i};
    if isstr(tmp), imP = tmp;       % images to extract data from
    elseif isstruct(tmp), vmat = tmp.mat;  % it's an spm_vol V struct
    elseif isscalar(tmp), df = tmp; % df to convert from t to z-scores
    elseif all(size(tmp) > 1), vmat = tmp;      % it's a SPM .mat matrix to be used with raw data instead of string img name
    end