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 CTF, 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'}

%

% See also FT_PREPROCESSING, FT_SENSLABEL, FT_MULTIPLOTER, FT_MULTIPLOTTFR,

% FT_SINGLEPLOTER, FT_SINGLEPLOTTFR

% Copyright (C) 2003-2021, Robert Oostenveld

%

% This file is part of FieldTrip, see http://www.fieldtriptoolbox.org

% 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/>.

%

% $Id$

% this is to avoid a recursion loop

persistent recursion

if isempty(recursion)

recursion = false;

end

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 = [];

end

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);

else

ft_error('please specify the data channels as a cell-array');

end

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;

end

datachannel = datachannel(sel);

if ~isempty(datachantype)

datachantype = datachantype(sel);

end

end

if isempty(desired)

% return an empty selection

channel = {};

return

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(:);

return

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);

return

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');

end

% 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

return

end

% 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'}';

labeleeg = datachannel(startsWith(datachannel, 'EEG')); % anything that starts with EEG

labeleog = datachannel(startsWith(datachannel, '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

continue;

end

if strcmp((channel{i}(1)), '-')

% skip channels to be excluded

continue;

end

rexp = sprintf('%s%s%s', '^', regexptranslate('wildcard',channel{i}), '$');

lreg = ~cellfun(@isempty, regexp(datachannel, rexp));

if any(lreg)

labelreg = labelreg | lreg;

findreg = [findreg; i];

end

end

if ~isempty(findreg)

findreg = unique(findreg); % remove multiple occurrences due to multiple wildcards

labelreg = datachannel(labelreg);

end

if isempty(senstype)

senstype = ft_senstype(datachannel);

end

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', 'ctf275_planar_combined', 'ctf151_planar_combined'}

% 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' )));

labelmeggrad = 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, 1));

];

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', 'bti248_planar_combined', 'bti148_planar_combined'}

% 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));

end

case {'itab153' 'itab28' 'itab28_old'}

% all itab MEG channels start with MAG

labelmeg = datachannel(strncmp('MAG', datachannel, length('MAG')));

case{'qzfm_gen2'}

% This is for use with QZFM_Gen2 Optically Pumped Magnetometers manufactured by QuSpin Inc.

% SPECS: https://quspin.com/qzfm-gen-2-update/

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:

% https://www.fieldtriptoolbox.org/getting_started/opm_fil/

labelmegtan = labelmeg(~cellfun(@isempty, regexp(labelmeg, '.*TAN$')));

labelmegrad = labelmeg(~cellfun(@isempty, regexp(labelmeg, '.*RAD$')));

otherwise

if ~isempty(datachantype)

labelmeg = datachannel(strncmp('meg', datachantype, 3));

labeleeg = datachannel(strncmp('eeg', datachantype, 3));

end

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

end

badchannel = ft_channelselection(badchannel, datachannel); % support exclusion of channel groups

end

% 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 occurrences of groups in the channel list

channel([

findall

findreg

findmeg

findemg

findecg

findeeg

findeeg1020

findeeg1010

findeeg1005

findeegchwilla

findeegbham

findeegref

findmegref

findmeggrad

findmegplanar

findmegmag

findeog

findmz

findml

findmr

findmlc

findmlf

findmlo

findmlp

findmlt

findmrc

findmrf

findmro

findmrp

findmrt

findmzc

findmzf

findmzo

findmzp

findlfp

findmua

findspike

findnirs

findgui

]) = [];

% 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);

end

% 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);

end

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);

end

% 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'));

end