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: fourier2crsspctrm.m
    path of file: ./repos/malini/Codes/deconvolution - model/spm8/external/fieldtrip/private
    
    the code of the file until where you have to start completion: function output = fourier2crsspctrm(cfg, freq)

% FOURIER2CRSSPCTRM transforms a fourier-containing freq-structure 
% into a crsspctrm-containing freq-structure, in which the
% powerspectra are also contained in the cross-spectra, being a 
% channelcombination of a channel with itself.
%
% Use as
%   [freq] = fourier2crsspctrm(cfg, freq)
%

    
function output = fourier2crsspctrm(cfg, freq)

% FOURIER2CRSSPCTRM transforms a fourier-containing freq-structure 
% into a crsspctrm-containing freq-structure, in which the
% powerspectra are also contained in the cross-spectra, being a 
% channelcombination of a channel with itself.
%
% Use as
%   [freq] = fourier2crsspctrm(cfg, freq)
%
% where you have the following configuration options:
%   cfg.channel    = cell-array with selection of channels,
%                    see CHANNELSELECTION for details
%   cfg.channelcmb = cell-array with selection of combinations between
%                    channels, see CHANNELCOMBINATION for details
%   cfg.keeptrials = 'yes' or 'no' (default)
%   cfg.foilim     = 2-element vector defining your frequency limits of 
%                    interest. By default the whole frequency range of the 
%                    input is taken.
%

% This file is part of FieldTrip, see http://www.ru.nl/neuroimaging/fieldtrip
% for the documentation and details.
%
%    FieldTrip is free software: you can redistribute it and/or modify
%    it under the terms of the GNU General Public License as published by
%    the Free Software Foundation, either version 3 of the License, or
%    (at your option) any later version.
%
%    FieldTrip is distributed in the hope that it will be useful,
%    but WITHOUT ANY WARRANTY; without even the implied warranty of
%    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
%    GNU General Public License for more details.
%
%    You should have received a copy of the GNU General Public License
%    along with FieldTrip. If not, see <http://www.gnu.org/licenses/>.
%
% $Id: fourier2crsspctrm.m 7123 2012-12-06 21:21:38Z roboos $

if ~isfield(cfg, 'channel'),     cfg.channel     = {'all'};                       end