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_dcm_compare.m
    path of file: ./repos/bspm/thirdparty/spm12
    
    the code of the file until where you have to start completion: function spm_dcm_compare(P)
% Compare two or more estimated models
% FORMAT spm_dcm_compare(P)
%
% P  - a char or cell array of DCM filenames
%__________________________________________________________________________
% Copyright (C) 2008 Wellcome Trust Centre for Neuroimaging

% Klaas Enno Stephan
% $Id: spm_dcm_compare.m 3363 2009-09-04 15:11:19Z christophe $


% Get DCM filenames

    
function spm_dcm_compare(P)
% Compare two or more estimated models
% FORMAT spm_dcm_compare(P)
%
% P  - a char or cell array of DCM filenames
%__________________________________________________________________________
% Copyright (C) 2008 Wellcome Trust Centre for Neuroimaging

% Klaas Enno Stephan
% $Id: spm_dcm_compare.m 3363 2009-09-04 15:11:19Z christophe $


% Get DCM filenames
%--------------------------------------------------------------------------
if ~nargin
    P = spm_select([2 inf],'^DCM.*\.mat$','select DCM*.mat files');
end