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_ssr_data.m
    path of file: ./repos/spm12/toolbox/dcm_meeg
    
    the code of the file until where you have to start completion: function DCM = spm_dcm_ssr_data(DCM)
% gets cross-spectral density data-features using a VAR model
% FORMAT DCM = spm_dcm_ssr_data(DCM)
% DCM    -  DCM structure
% requires
%
%    DCM.xY.Dfile        - name of data file
%    DCM.M.U             - channel subspace
%    DCM.options.trials  - trial to evaluate
%    DCM.options.Tdcm    - time limits
%    DCM.options.Fdcm    - frequency limits
%    DCM.options.D       - Down-sampling
%
% sets
%
%    DCM.xY.pst     - Peristimulus Time [ms] sampled
%    DCM.xY.dt      - sampling in seconds [s] (down-sampled)
%    DCM.xY.U       - channel subspace
%    DCM.xY.y       - cross spectral density over sources
%    DCM.xY.csd     - cross spectral density over sources
%    DCM.xY.It      - Indices of time bins
%    DCM.xY.Ic      - Indices of good channels
%    DCM.xY.Hz      - Frequency bins
%    DCM.xY.code    - trial codes evaluated
%__________________________________________________________________________
% Copyright (C) 2008 Wellcome Trust Centre for Neuroimaging
 
% Karl Friston
% $Id: spm_dcm_ssr_data.m 5082 2012-11-28 20:25:37Z karl $

    
function DCM = spm_dcm_ssr_data(DCM)
% gets cross-spectral density data-features using a VAR model
% FORMAT DCM = spm_dcm_ssr_data(DCM)
% DCM    -  DCM structure
% requires
%
%    DCM.xY.Dfile        - name of data file
%    DCM.M.U             - channel subspace
%    DCM.options.trials  - trial to evaluate
%    DCM.options.Tdcm    - time limits
%    DCM.options.Fdcm    - frequency limits
%    DCM.options.D       - Down-sampling
%
% sets
%
%    DCM.xY.pst     - Peristimulus Time [ms] sampled
%    DCM.xY.dt      - sampling in seconds [s] (down-sampled)
%    DCM.xY.U       - channel subspace
%    DCM.xY.y       - cross spectral density over sources
%    DCM.xY.csd     - cross spectral density over sources
%    DCM.xY.It      - Indices of time bins
%    DCM.xY.Ic      - Indices of good channels
%    DCM.xY.Hz      - Frequency bins
%    DCM.xY.code    - trial codes evaluated
%__________________________________________________________________________
% Copyright (C) 2008 Wellcome Trust Centre for Neuroimaging
 
% Karl Friston
% $Id: spm_dcm_ssr_data.m 5082 2012-11-28 20:25:37Z karl $
 
% Set defaults and Get D filename
%-------------------------------------------------------------------------
try
    Dfile = DCM.xY.Dfile;
catch
    errordlg('Please specify data and trials');
    error('')
end