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: spm_global.m
    path of file: ./repos/spm
    
    the code of the file until where you have to start completion: function GX = spm_global(V)
% Compute the global mean for a volume image - a compiled routine
% FORMAT GX = spm_global(V)
% V   - image handle structure
% GX  - global mean
%__________________________________________________________________________
%
% spm_global returns the mean counts integrated over all the slices from
% the volume.
%
% The mean is estimated after discounting voxels outside the object using
% a criteria of greater than > (global mean)/8.
%__________________________________________________________________________

% Anonymous

    
function GX = spm_global(V)
% Compute the global mean for a volume image - a compiled routine
% FORMAT GX = spm_global(V)
% V   - image handle structure
% GX  - global mean
%__________________________________________________________________________
%
% spm_global returns the mean counts integrated over all the slices from
% the volume.
%
% The mean is estimated after discounting voxels outside the object using
% a criteria of greater than > (global mean)/8.
%__________________________________________________________________________

% Anonymous
% Copyright (C) 1996-2022 Wellcome Centre for Human Neuroimaging


%-This is merely the help file for the compiled routine
error('spm_global.c not compiled - see Makefile')

% GX = zeros(numel(V),1);
% 
% for i=1:numel(V)
%     
%     D     = spm_data_read(V(i));
%     
%     iD    = isfinite(D);
%     
%     S     = mean(D(iD)) / 8;
%     
%     GX(i) = mean(D(iD & (D > S)));
%     
% end