filter_eeg

 Filter EEG data

 Copyright (C) 2011, ATR All Rights Reserved.
 License : New BSD License(see VBMEG_LICENSE.txt)

0001 function filter_eeg(p)
0002 % Filter EEG data
0003 %
0004 % Copyright (C) 2011, ATR All Rights Reserved.
0005 % License : New BSD License(see VBMEG_LICENSE.txt)
0006 
0007 disp(mfilename);
0008 
0009 % Set parameters
0010 ch_filter=1:65;
0011 ch_trigger=66;
0012 Nsample_trig=100;
0013 
0014 parm.bias_flg = p.bias_flg; % Bias correction (=0/1/2: OFF/Bias/Linear)
0015 parm.highpass = p.highpass; % Highpass filter cutoff frequency [Hz]
0016 parm.lowpass = p.lowpass; % Lowpass  filter cutoff frequency [Hz]
0017 parm.fsamp = p.fsamp;% down sampling frequency [Hz]
0018 parm.highpass_online = p.highpass_online; % order of online highpass filter (0=eegfilt)
0019 parm.lowpass_online = p.lowpass_online; % order of online lowpass filter (0=eegfilt)
0020 
0021 % Set output directory
0022 output_dir=fullfile(p.proj_root, p.eeg_dirname, p.filter_dirname);
0023 if exist(output_dir, 'dir') ~= 7
0024     mkdir(output_dir);
0025 end
0026 
0027 for file=1:length(p.file_list)
0028     disp(p.file_list{file})
0029     
0030     % Load EEG data
0031     eeg_file=fullfile(p.proj_root, p.eeg_dirname, p.load_dirname, [p.file_list{file} '.eeg.mat']);
0032     load(eeg_file)
0033     
0034     % Modify trigger channel
0035     t=1;
0036     while t<=EEGinfo.Nsample
0037         if eeg_data(ch_trigger,t)>0.5
0038             eeg_data(ch_trigger,t:t+Nsample_trig-1)=1;
0039             t=t+Nsample_trig;
0040         end
0041         t=t+1;
0042     end
0043     
0044     % Lowpass filter
0045     eeg_data(ch_filter,:)=eegfilt(eeg_data(ch_filter,:),EEGinfo.SampleFrequency,0,parm.lowpass);
0046     
0047     % Down sampling
0048     if EEGinfo.SampleFrequency~=parm.fsamp
0049         eeg_data = vb_convert_freq(eeg_data, EEGinfo.SampleFrequency, parm.fsamp);
0050     end
0051     EEGinfo.SampleFrequency=parm.fsamp;
0052     EEGinfo.Nsample=size(eeg_data,2);
0053     
0054     % Highpass filter
0055     eeg_data(ch_filter,:)=eegfilt(eeg_data(ch_filter,:),EEGinfo.SampleFrequency,parm.highpass,0);
0056     
0057     % Save filtered EEG data
0058     filtered_file=fullfile(output_dir, [p.file_list{file} '.eeg.mat']);
0059     save(filtered_file, 'eeg_data', 'EEGinfo', 'Measurement')
0060 end