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.

 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'}

 See also FT_PREPROCESSING, FT_SENSLABEL, FT_MULTIPLOTER, FT_MULTIPLOTTFR,
 FT_SINGLEPLOTER, FT_SINGLEPLOTTFR