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function [channel] = ft_channelselection(desired, datachannel, senstype)
% FT_CHANNELSELECTION makes a selection of EEG and/or MEG channel labels. This
% function translates the user-specified list of channels into channel labels as they
% occur in the data. This channel selection procedure can be used throughout
% FieldTrip.
% You can specify a mixture of real channel labels and of special strings, or index
% numbers that will be replaced by the corresponding channel labels. Channels that
% are not present in the raw datafile are automatically removed from the channel
% list.
% The order of the channels in the list that is returned corresponds to the order in
% the data.
% E.g. the desired input specification can be:
% 'all' is replaced by all channels in the datafile
% 'gui' this will pop up a graphical user interface to select the channels
% 'C*' is replaced by all channels that match the wildcard, e.g. C1, C2, C3, ...
% '*1' is replaced by all channels that match the wildcard, e.g. C1, P1, F1, ...
% 'M*1' is replaced by all channels that match the wildcard, e.g. MEG0111, MEG0131, MEG0131, ...
% 'meg' is replaced by all MEG channels (works for CTF, 4D, Neuromag and Yokogawa)
% 'megref' is replaced by all MEG reference channels (works for CTF and 4D)
% 'meggrad' is replaced by all MEG gradiometer channels (works for Yokogawa and Neuromag306)
% 'megplanar' is replaced by all MEG planar gradiometer channels (works for Neuromag306)
% 'megmag' is replaced by all MEG magnetometer channels (works for Yokogawa and Neuromag306)
% 'eeg' is replaced by all recognized EEG channels (this is system dependent)
% 'eeg1020' is replaced by 'Fp1', 'Fpz', 'Fp2', 'F7', 'F3', ...
% 'eog' is replaced by all recognized EOG channels
% 'ecg' is replaced by all recognized ECG channels
% 'nirs' is replaced by all channels recognized as NIRS channels
% 'emg' is replaced by all channels in the datafile starting with 'EMG'
% 'lfp' is replaced by all channels in the datafile starting with 'lfp'
% 'mua' is replaced by all channels in the datafile starting with 'mua'
% 'spike' is replaced by all channels in the datafile starting with 'spike'
% 10 is replaced by the 10th channel in the datafile
% Other channel groups are
% 'EEG1010' with approximately 90 electrodes
% 'EEG1005' with approximately 350 electrodes
% 'EEGREF' for mastoid and ear electrodes (M1, M2, LM, RM, A1, A2)
% 'MZ' for MEG zenith
% 'ML' for MEG left
% 'MR' for MEG right
% 'MLx', 'MRx' and 'MZx' with x=C,F,O,P,T for left/right central, frontal, occipital, parietal and temporal
% You can also exclude channels or channel groups using the following syntax
% {'all', '-POz', '-Fp1', -EOG'}
% Copyright (C) 2003-2021, Robert Oostenveld
% This file is part of FieldTrip, see
% 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
% 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 <>.
% $Id$
% this is to avoid a recursion loop
persistent recursion
if isempty(recursion)
recursion = false;
if nargin<3
% the actual senstype will be determined further down
% postponing the detection speeds up some common use patterns, such as 'all' and []
senstype = [];
if iscell(datachannel)
% this is the expected format of the input
datachantype = {};
elseif ischar(datachannel)
datachannel = {datachannel};
datachantype = {};
elseif isstruct(datachannel) && isfield(datachannel, 'label')
% it looks like a header structure
hdr = datachannel;
datachannel = hdr.label;
datachantype = ft_chantype(hdr);
ft_error('please specify the data channels as a cell-array');
if length(datachannel)~=length(unique(datachannel))
ft_warning('discarding non-unique channel names');
sel = false(size(datachannel));
for i=1:length(datachannel)
sel(i) = sum(strcmp(datachannel, datachannel{i}))==1;
datachannel = datachannel(sel);
if ~isempty(datachantype)
datachantype = datachantype(sel);
if isempty(desired)
% return an empty selection
channel = {};
elseif isequal(desired, 'all') || isequal(desired, {'all'})
% this is a very common use pattern that can be dealt with quickly
% ensure that the output is a column vector
channel = datachannel(:);
elseif isnumeric(desired)
% remove channels that fall outside the range
desired = desired(desired>=1 & desired<=numel(datachannel));
% change the numeric index into the channel name
channel = datachannel(desired);
elseif ischar(desired)
% ensure that a single input argument like 'all' also works
desired = {desired};
elseif ~iscell(desired)
ft_error('please specify the desired channels as a cell-array or a string');
% start with the list of desired channels, this will be pruned/expanded further down
channel = desired;
% ensure that both inputs are column vectors
channel = channel(:);
datachannel = datachannel(:);
% remove channels that occur more than once, this sorts the channels alphabetically
[channel, indx] = unique(channel);
% undo the sorting, make the order identical to that of the data channels
[dum, indx] = sort(indx);
channel = channel(indx);
[dataindx, chanindx] = match_str(datachannel, channel);
if length(chanindx)==length(channel)
% there is a perfect match between the channels and the datachannels, only some reordering is needed
channel = channel(chanindx);
% no need to look at channel groups
% initialize all the system-specific variables to empty
labelall = {};
labelreg = {};
labelmeg = {};
labelecg = {};
labelemg = {};
labeleeg = {};
label102 = {};
label101 = {};
label100 = {};
labelchwilla = {};
labelbha = {};
labelref = {};
labelmegref = {};
labelmeggrad = {};
labelmegplanar = {};
labelmegmag = {};
labelmegrefa = {};
labelmegrefc = {};
labelmegrefg = {};
labelmegrefl = {};
labelmegrefr = {};
labelmegrefm = {};
labeleog = {};
labelmz = {};
labelml = {};
labelmr = {};
labelmlc = {};
labelmlf = {};
labelmlo = {};
labelmlp = {};
labelmlt = {};
labelmrc = {};
labelmrf = {};
labelmro = {};
labelmrp = {};
labelmrt = {};
labelmzc = {};
labelmzf = {};
labelmzo = {};
labelmzp = {};
labellfp = {};
labelmua = {};
labelspike = {};
labelnirs = {};
% define the known groups with channel labels
labelall = datachannel;
label1020 = ft_senslabel('eeg1020'); % use external helper function
label1010 = ft_senslabel('eeg1010'); % use external helper function
label1005 = ft_senslabel('eeg1005'); % use external helper function
labelchwilla = {'Fz', 'Cz', 'Pz', 'F7', 'F8', 'LAT', 'RAT', 'LT', 'RT', 'LTP', 'RTP', 'OL', 'OR', 'FzA', 'Oz', 'F7A', 'F8A', 'F3A', 'F4A', 'F3', 'F4', 'P3', 'P4', 'T5', 'T6', 'P3P', 'P4P'}';
labelbham = {'P9', 'PPO9h', 'PO7', 'PPO5h', 'PPO3h', 'PO5h', 'POO9h', 'PO9', 'I1', 'OI1h', 'O1', 'POO1', 'PO3h', 'PPO1h', 'PPO2h', 'POz', 'Oz', 'Iz', 'I2', 'OI2h', 'O2', 'POO2', 'PO4h', 'PPO4h', 'PO6h', 'POO10h', 'PO10', 'PO8', 'PPO6h', 'PPO10h', 'P10', 'P8', 'TPP9h', 'TP7', 'TTP7h', 'CP5', 'TPP7h', 'P7', 'P5', 'CPP5h', 'CCP5h', 'CP3', 'P3', 'CPP3h', 'CCP3h', 'CP1', 'P1', 'Pz', 'CPP1h', 'CPz', 'CPP2h', 'P2', 'CPP4h', 'CP2', 'CCP4h', 'CP4', 'P4', 'P6', 'CPP6h', 'CCP6h', 'CP6', 'TPP8h', 'TP8', 'TPP10h', 'T7', 'FTT7h', 'FT7', 'FC5', 'FCC5h', 'C5', 'C3', 'FCC3h', 'FC3', 'FC1', 'C1', 'CCP1h', 'Cz', 'FCC1h', 'FCz', 'FFC1h', 'Fz', 'FFC2h', 'FC2', 'FCC2h', 'CCP2h', 'C2', 'C4', 'FCC4h', 'FC4', 'FC6', 'FCC6h', 'C6', 'TTP8h', 'T8', 'FTT8h', 'FT8', 'FT9', 'FFT9h', 'F7', 'FFT7h', 'FFC5h', 'F5', 'AFF7h', 'AF7', 'AF5h', 'AFF5h', 'F3', 'FFC3h', 'F1', 'AF3h', 'Fp1', 'Fpz', 'Fp2', 'AFz', 'AF4h', 'F2', 'FFC4h', 'F4', 'AFF6h', 'AF6h', 'AF8', 'AFF8h', 'F6', 'FFC6h', 'FFT8h', 'F8', 'FFT10h', 'FT10'};
labelref = {'M1', 'M2', 'LM', 'RM', 'A1', 'A2'}';
labeleog = datachannel(strncmp('EOG', datachannel, length('EOG'))); % anything that starts with EOG
labeleog = [labeleog(:); {'HEOG', 'VEOG', 'VEOG-L', 'VEOG-R', 'hEOG', 'vEOG', 'Eye_Ver', 'Eye_Hor'}']; % or any of these
labelecg = datachannel(strncmp('ECG', datachannel, length('ECG')));
labelemg = datachannel(strncmp('EMG', datachannel, length('EMG')));
labellfp = datachannel(strncmp('lfp', datachannel, length('lfp')));
labelmua = datachannel(strncmp('mua', datachannel, length('mua')));
labelspike = datachannel(strncmp('spike', datachannel, length('spike')));
% for NIRS there are multiple options, either using the terminology transmitter/receiver versus source/detector, and then with either order of the two
option1 = ~cellfun(@isempty, regexp(datachannel, sprintf('%s%s', regexptranslate('wildcard','Rx*-Tx*[*]'), '$')));
option2 = ~cellfun(@isempty, regexp(datachannel, sprintf('%s%s', regexptranslate('wildcard','Tx*-Rx*[*]'), '$')));
option3 = ~cellfun(@isempty, regexp(datachannel, sprintf('%s%s', regexptranslate('wildcard','D*-S*[*]'), '$')));
option4 = ~cellfun(@isempty, regexp(datachannel, sprintf('%s%s', regexptranslate('wildcard','S*-D*[*]'), '$')));
labelnirs = datachannel(option1 | option2 | option3 | option4);
% use regular expressions to deal with the wildcards
labelreg = false(size(datachannel));
findreg = [];
for i=1:length(channel)
if length(channel{i}) < 1
if strcmp((channel{i}(1)), '-')
% skip channels to be excluded
rexp = sprintf('%s%s%s', '^', regexptranslate('wildcard',channel{i}), '$');
lreg = ~cellfun(@isempty, regexp(datachannel, rexp));
if any(lreg)
labelreg = labelreg | lreg;
findreg = [findreg; i];
if ~isempty(findreg)
findreg = unique(findreg); % remove multiple occurances due to multiple wildcards
labelreg = datachannel(labelreg);
if isempty(senstype)
senstype = ft_senstype(datachannel);
switch senstype
case {'yokogawa', 'yokogawa160', 'yokogawa160_planar', 'yokogawa64', 'yokogawa64_planar', 'yokogawa440', 'yokogawa440_planar'}
% Yokogawa axial gradiometers channels start with AG, hardware planar gradiometer
% channels start with PG, magnetometers start with M
megax = strncmp('AG', datachannel, length('AG'));
megpl = strncmp('PG', datachannel, length('PG'));
megmag = strncmp('M', datachannel, length('M' ));
megind = logical( megax + megpl + megmag);
labelmeg = datachannel(megind);
labelmegmag = datachannel(megmag);
labelmeggrad = datachannel(megax | megpl);
% labeleeg = datachannel(strncmp('EEG', datachannel, length('EEG')));
eeg_A = myregexp('^A[^G]*[0-9hzZ]$', datachannel);
eeg_P = myregexp('^P[^G]*[0-9hzZ]$', datachannel);
eeg_T = myregexp('^T[^R]*[0-9hzZ]$', datachannel);
eeg_E = myregexp('^E$', datachannel);
eeg_Z = myregexp('^[zZ]$', datachannel);
eeg_M = myregexp('^M[0-9]$', datachannel);
eeg_O = myregexp('^[BCFION]\w*[0-9hzZ]$', datachannel);
eeg_EEG = myregexp('^EEG[0-9][0-9][0-9]$', datachannel);
eegind = logical( eeg_A + eeg_P + eeg_T + eeg_E + eeg_Z + eeg_M + eeg_O + eeg_EEG );
clear eeg_A eeg_P eeg_T eeg_E eeg_Z eeg_M eeg_O eeg_EEG
labeleeg = datachannel(eegind);
labeleog = [ labeleog(:); datachannel(myregexp('^EO[0-9]$', datachannel)) ]; % add 'EO'
labelecg = [ labelecg(:); datachannel(myregexp('^X[0-9]$', datachannel)) ]; % add 'X'
case {'ctf64'}
labelml = datachannel(~cellfun(@isempty, regexp(datachannel, '^SL'))); % left MEG channels
labelmr = datachannel(~cellfun(@isempty, regexp(datachannel, '^SR'))); % right MEG channels
labelmeg = cat(1, labelml, labelmr);
labelmegref = [datachannel(strncmp('B' , datachannel, 1));
datachannel(strncmp('G' , datachannel, 1));
datachannel(strncmp('P' , datachannel, 1));
datachannel(strncmp('Q' , datachannel, 1));
datachannel(strncmp('R' , datachannel, length('G' )))];
case {'ctf', 'ctf275', 'ctf151', 'ctf275_planar', 'ctf151_planar'}
% all CTF MEG channels start with "M"
% all CTF reference channels start with B, G, P, Q or R
% all CTF EEG channels start with "EEG"
labelmeg = datachannel(strncmp('M' , datachannel, length('M' )));
labelmegref = [datachannel(strncmp('B' , datachannel, 1));
datachannel(strncmp('G' , datachannel, 1));
datachannel(strncmp('P' , datachannel, 1));
datachannel(strncmp('Q' , datachannel, 1));
datachannel(strncmp('R' , datachannel, length('G' )))];
labeleeg = datachannel(strncmp('EEG', datachannel, length('EEG')));
% Not sure whether this should be here or outside the switch or
% whether these specifications should be supported for systems
% other than CTF.
labelmz = datachannel(strncmp('MZ' , datachannel, length('MZ' ))); % central MEG channels
labelml = datachannel(strncmp('ML' , datachannel, length('ML' ))); % left MEG channels
labelmr = datachannel(strncmp('MR' , datachannel, length('MR' ))); % right MEG channels
labelmlc = datachannel(strncmp('MLC', datachannel, length('MLC')));
labelmlf = datachannel(strncmp('MLF', datachannel, length('MLF')));
labelmlo = datachannel(strncmp('MLO', datachannel, length('MLO')));
labelmlp = datachannel(strncmp('MLP', datachannel, length('MLP')));
labelmlt = datachannel(strncmp('MLT', datachannel, length('MLT')));
labelmrc = datachannel(strncmp('MRC', datachannel, length('MRC')));
labelmrf = datachannel(strncmp('MRF', datachannel, length('MRF')));
labelmro = datachannel(strncmp('MRO', datachannel, length('MRO')));
labelmrp = datachannel(strncmp('MRP', datachannel, length('MRP')));
labelmrt = datachannel(strncmp('MRT', datachannel, length('MRT')));
labelmzc = datachannel(strncmp('MZC', datachannel, length('MZC')));
labelmzf = datachannel(strncmp('MZF', datachannel, length('MZF')));
labelmzo = datachannel(strncmp('MZO', datachannel, length('MZO')));
labelmzp = datachannel(strncmp('MZP', datachannel, length('MZP')));
case {'bti', 'bti248', 'bti248grad', 'bti148', 'bti248_planar', 'bti148_planar'}
% all 4D-BTi MEG channels start with "A"
% all 4D-BTi reference channels start with M or G
labelmeg = datachannel(myregexp('^A[0-9]+$', datachannel));
labelmegref = [datachannel(myregexp('^M[CLR][xyz][aA]*$', datachannel)); datachannel(myregexp('^G[xyz][xyz]A$', datachannel)); datachannel(myregexp('^M[xyz][aA]*$', datachannel))];
labelmegrefa = datachannel(~cellfun(@isempty,strfind(datachannel, 'a')));
labelmegrefc = datachannel(strncmp('MC', datachannel, 2));
labelmegrefg = datachannel(myregexp('^G[xyz][xyz]A$', datachannel));
labelmegrefl = datachannel(strncmp('ML', datachannel, 2));
labelmegrefr = datachannel(strncmp('MR', datachannel, 2));
labelmegrefm = datachannel(myregexp('^M[xyz][aA]*$', datachannel));
case {'neuromag122' 'neuromag122alt', 'neuromag122_combined'}
% all neuromag MEG channels start with MEG
% all neuromag EEG channels start with EEG
labelmeg = datachannel(strncmp('MEG', datachannel, length('MEG')));
labeleeg = datachannel(strncmp('EEG', datachannel, length('EEG')));
case {'neuromag306' 'neuromag306alt', 'neuromag306_combined'}
% all neuromag MEG channels start with MEG
% all neuromag EEG channels start with EEG
% all neuromag306 gradiometers follow pattern MEG*2,MEG*3
% all neuromag306 magnetometers follow pattern MEG*1
labelmeg = datachannel(strncmp('MEG', datachannel, length('MEG')));
labeleeg = datachannel(strncmp('EEG', datachannel, length('EEG')));
labelmeggrad = labelmeg(~cellfun(@isempty, regexp(labelmeg, '^MEG.*[23]$')));
labelmegmag = labelmeg(~cellfun(@isempty, regexp(labelmeg, '^MEG.*1$')));
labelmegplanar = labelmeggrad;
case {'ant128', 'biosemi64', 'biosemi128', 'biosemi256', 'egi32', 'egi64', 'egi128', 'egi256', 'eeg1020', 'eeg1010', 'eeg1005', 'ext1020'}
if ~ft_senstype(datachannel, 'unknown')
% use an external helper function to define the list with EEG channel names
labeleeg = ft_senslabel(ft_senstype(datachannel));
case {'itab153' 'itab28' 'itab28_old'}
% all itab MEG channels start with MAG
labelmeg = datachannel(strncmp('MAG', datachannel, length('MAG')));
% This is for use with QZFM_Gen2 Optically Pumped Magnetometers
% manufactured by QuSpin Inc.
labelmeg = datachannel(strncmp('meg', datachantype, 3));
labelmegref = datachannel(strncmp('refmag', datachantype, 3));
% All channels measuring tangential fields are end with TAN
% All channels measuring radial fields are end with RAD
% This is specific to data collected from UCL. Also see:
labelmegtan = labelmeg(~cellfun(@isempty, regexp(labelmeg, '.*TAN$')));
labelmegrad = labelmeg(~cellfun(@isempty, regexp(labelmeg, '.*RAD$')));
if ~isempty(datachantype)
labelmeg = datachannel(strncmp('meg', datachantype, 3));
labeleeg = datachannel(strncmp('eeg', datachantype, 3));
end % switch ft_senstype
% figure out if there are bad channels or channel groups that should be excluded
findbadchannel = strncmp('-', channel, length('-')); % bad channels start with '-'
badchannel = channel(findbadchannel);
if ~isempty(badchannel)
for i=1:length(badchannel)
badchannel{i} = badchannel{i}(2:end); % remove the '-' from the channel label
badchannel = ft_channelselection(badchannel, datachannel); % support exclusion of channel groups
% determine if any of the known groups is mentioned in the channel list
findall = find(strcmp(channel, 'all'));
% findreg (for the wildcards) is dealt with in the channel group specification above
findmeg = find(strcmpi(channel, 'MEG'));
findemg = find(strcmpi(channel, 'EMG'));
findecg = find(strcmpi(channel, 'ECG'));
findeeg = find(strcmpi(channel, 'EEG'));
findeeg1020 = find(strcmpi(channel, 'EEG1020'));
findeeg1010 = find(strcmpi(channel, 'EEG1010'));
findeeg1005 = find(strcmpi(channel, 'EEG1005'));
findeegchwilla = find(strcmpi(channel, 'EEGCHWILLA'));
findeegbham = find(strcmpi(channel, 'EEGBHAM'));
findeegref = find(strcmpi(channel, 'EEGREF'));
findmegref = find(strcmpi(channel, 'MEGREF'));
findmeggrad = find(strcmpi(channel, 'MEGGRAD'));
findmegplanar = find(strcmpi(channel, 'MEGPLANAR'));
findmegmag = find(strcmpi(channel, 'MEGMAG'));
findmegrefa = find(strcmpi(channel, 'MEGREFA'));
findmegrefc = find(strcmpi(channel, 'MEGREFC'));
findmegrefg = find(strcmpi(channel, 'MEGREFG'));
findmegrefl = find(strcmpi(channel, 'MEGREFL'));
findmegrefr = find(strcmpi(channel, 'MEGREFR'));
findmegrefm = find(strcmpi(channel, 'MEGREFM'));
findmegtan = find(strcmpi(channel, 'MEGTAN'));
findmegrad = find(strcmpi(channel, 'MEGRAD'));
findeog = find(strcmpi(channel, 'EOG'));
findmz = find(strcmp(channel, 'MZ' ));
findml = find(strcmp(channel, 'ML' ));
findmr = find(strcmp(channel, 'MR' ));
findmlc = find(strcmp(channel, 'MLC'));
findmlf = find(strcmp(channel, 'MLF'));
findmlo = find(strcmp(channel, 'MLO'));
findmlp = find(strcmp(channel, 'MLP'));
findmlt = find(strcmp(channel, 'MLT'));
findmrc = find(strcmp(channel, 'MRC'));
findmrf = find(strcmp(channel, 'MRF'));
findmro = find(strcmp(channel, 'MRO'));
findmrp = find(strcmp(channel, 'MRP'));
findmrt = find(strcmp(channel, 'MRT'));
findmzc = find(strcmp(channel, 'MZC'));
findmzf = find(strcmp(channel, 'MZF'));
findmzo = find(strcmp(channel, 'MZO'));
findmzp = find(strcmp(channel, 'MZP'));
findnirs = find(strcmpi(channel, 'NIRS'));
findlfp = find(strcmpi(channel, 'lfp'));
findmua = find(strcmpi(channel, 'mua'));
findspike = find(strcmpi(channel, 'spike'));
findgui = find(strcmpi(channel, 'gui'));
% remove any occurences of groups in the channel list
]) = [];
% add the full channel labels to the channel list
if findall, channel = [channel; labelall]; end
if findreg, channel = [channel; labelreg]; end
if findmeg, channel = [channel; labelmeg]; end
if findecg, channel = [channel; labelecg]; end
if findemg, channel = [channel; labelemg]; end
if findeeg, channel = [channel; labeleeg]; end
if findeeg1020, channel = [channel; label1020]; end
if findeeg1010, channel = [channel; label1010]; end
if findeeg1005, channel = [channel; label1005]; end
if findeegchwilla, channel = [channel; labelchwilla]; end
if findeegbham, channel = [channel; labelbham]; end
if findeegref, channel = [channel; labelref]; end
if findmegref, channel = [channel; labelmegref]; end
if findmeggrad, channel = [channel; labelmeggrad]; end
if findmegplanar, channel = [channel; labelmegplanar]; end
if findmegmag, channel = [channel; labelmegmag]; end
if findmegrefa, channel = [channel; labelmegrefa]; end
if findmegrefc, channel = [channel; labelmegrefc]; end
if findmegrefg, channel = [channel; labelmegrefg]; end
if findmegrefl, channel = [channel; labelmegrefl]; end
if findmegrefr, channel = [channel; labelmegrefr]; end
if findmegrefm, channel = [channel; labelmegrefm]; end
if findmegtan, channel = [channel; labelmegtan]; end
if findmegrad, channel = [channel; labelmegrad]; end
if findeog, channel = [channel; labeleog]; end
if findmz , channel = [channel; labelmz ]; end
if findml , channel = [channel; labelml ]; end
if findmr , channel = [channel; labelmr ]; end
if findmlc, channel = [channel; labelmlc]; end
if findmlf, channel = [channel; labelmlf]; end
if findmlo, channel = [channel; labelmlo]; end
if findmlp, channel = [channel; labelmlp]; end
if findmlt, channel = [channel; labelmlt]; end
if findmrc, channel = [channel; labelmrc]; end
if findmrf, channel = [channel; labelmrf]; end
if findmro, channel = [channel; labelmro]; end
if findmrp, channel = [channel; labelmrp]; end
if findmrt, channel = [channel; labelmrt]; end
if findmzc, channel = [channel; labelmzc]; end
if findmzf, channel = [channel; labelmzf]; end
if findmzo, channel = [channel; labelmzo]; end
if findmzp, channel = [channel; labelmzp]; end
if findlfp, channel = [channel; labellfp]; end
if findmua, channel = [channel; labelmua]; end
if findspike, channel = [channel; labelspike]; end
if findnirs, channel = [channel; labelnirs]; end
% remove channel labels that have been excluded by the user
badindx = match_str(channel, badchannel);
channel(badindx) = [];
% remove channel labels that are not present in the data
chanindx = match_str(channel, datachannel);
channel = channel(chanindx);
if findgui
indx = select_channel_list(datachannel, match_str(datachannel, channel), 'Select channels');
channel = datachannel(indx);
% remove channels that occur more than once, this sorts the channels alphabetically
channel = unique(channel);
if isempty(channel) && ~recursion
% try whether only lowercase channel labels makes a difference
recursion = true;
channel = ft_channelselection(desired, lower(datachannel));
recursion = false;
% undo the conversion to lowercase, this sorts the channels alphabetically
[c, ia, ib] = intersect(channel, lower(datachannel));
channel = datachannel(ib);
if isempty(channel) && ~recursion
% try whether only uppercase channel labels makes a difference
recursion = true;
channel = ft_channelselection(desired, upper(datachannel));
recursion = false;
% undo the conversion to uppercase, this sorts the channels alphabetically
[c, ia, ib] = intersect(channel, lower(datachannel));
channel = datachannel(ib);
% undo the sorting, make the order identical to that of the data channels
[tmp, indx] = match_str(datachannel, channel);
channel = channel(indx);
% helper function
function match = myregexp(pat, list)
match = false(size(list));
for i=1:numel(list)
match(i) = ~isempty(regexp(list{i}, pat, 'once'));