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: mars_options.m
    path of file: ./repos/malini/Codes/deconvolution - model/spm8/marsbar-0.44
    
    the code of the file until where you have to start completion: function [mars, msgstr] = mars_options(optstr, mars, cfg_fname)
% options utility routines
% FORMAT [mars msgstr] = mars_options
    
function for ROI data
  mars.statistics.sumfunc = 'mean';
  
  % flag to indicate voxel data should be used to calculate filter
  mars.statistics.voxfilter = 0;

  % option to say if images should be flipped when converting
  % to and from spm99 designs
  mars.statistics.flip_option = mars_veropts('flip_option');

  % Whether to refresh contrast structure when loading designs
  mars.statistics.refresh_contrasts = 1;
  
  % Difference function to calculate % signal change
  mars.events.diff_func = 'abs max';
  
% --------------------------------------------------
 case 'edit'
  
  % Edit defaults.  See 'basedefaults' option for other defaults
  defarea = cfg_fname;  % third arg is defaults area, if specified
  if isempty(defarea)
    % get defaults area
    [Finter,Fgraph,CmdLine] = spm('FnUIsetup','MarsBar Defaults');

    defarea = char(...
      spm_input('Defaults area', '+1', 'm',{optlabs{:} 'Quit'},...
		{optfields{:} 'quit'},length(optfields)+1));
  end