rm_chan

 rm_chan() - Removes one or more channels (e.g., 'HEOG') from an EEGLAB 
             EEG variable.  Unlike EEGLAB functions for removing channels,
             rm_chan.m is aware of MATLABmk fields (e.g., those pertaining
             to cal pulse information) and it will adjust them for the
             deleted channel(s).
    
 Usage:
  >> EEG=rm_chan(EEG,chan_name,force);

 Required Inputs:
   EEG       - EEGLAB EEG struct variable
   chan_name - [string or cell array of strings] Name(s) of channel(s) to
               be removed (e.g., 'HEOG' or {'HEOG','lle','rle'})

 Optional Input:
   force     - [0 or 1] If 1, any information pertaining to ICA will be
               automatically removed from the EEG variable.  If 0, the 
               user will first be asked if she/he wants to erase ICA 
               information (if ICA has been performed on this EEG variable).
               {default: 0}

 Output:
   EEG       - Same as the input EEG variable but with information for
               requested channels removed.

 Example:
 >>EEG=rm_chan(EEG,'HEOG');

 Author:
 David Groppe
 Kutaslab, 7/2010

0001 % rm_chan() - Removes one or more channels (e.g., 'HEOG') from an EEGLAB
0002 %             EEG variable.  Unlike EEGLAB functions for removing channels,
0003 %             rm_chan.m is aware of MATLABmk fields (e.g., those pertaining
0004 %             to cal pulse information) and it will adjust them for the
0005 %             deleted channel(s).
0006 %
0007 % Usage:
0008 %  >> EEG=rm_chan(EEG,chan_name,force);
0009 %
0010 % Required Inputs:
0011 %   EEG       - EEGLAB EEG struct variable
0012 %   chan_name - [string or cell array of strings] Name(s) of channel(s) to
0013 %               be removed (e.g., 'HEOG' or {'HEOG','lle','rle'})
0014 %
0015 % Optional Input:
0016 %   force     - [0 or 1] If 1, any information pertaining to ICA will be
0017 %               automatically removed from the EEG variable.  If 0, the
0018 %               user will first be asked if she/he wants to erase ICA
0019 %               information (if ICA has been performed on this EEG variable).
0020 %               {default: 0}
0021 %
0022 % Output:
0023 %   EEG       - Same as the input EEG variable but with information for
0024 %               requested channels removed.
0025 %
0026 % Example:
0027 % >>EEG=rm_chan(EEG,'HEOG');
0028 %
0029 % Author:
0030 % David Groppe
0031 % Kutaslab, 7/2010
0032 
0033 function EEG=rm_chan(EEG,chan_name,force)
0034 
0035 if ~iscell(chan_name),
0036     chan_names{1}=chan_name;
0037 elseif ischar(chan_name)
0038    chan_names=chan_name; 
0039 else
0040    error('Argument chan_name needs to be a string or cell array of strings.'); 
0041 end
0042 
0043 if nargin<3.
0044    force=0; 
0045 end
0046 
0047 fldnms=fieldnames(EEG);
0048 
0049 %Ask about ICA overwrite
0050 if ~isempty(EEG.icawinv) && ~force,
0051    fprintf('** Warning **\n');
0052    fprintf('The ICA decomposition stored in this EEG variable will be erased if you proceed.\n');
0053    fprintf('The decomposition will no longer be valid since you are removing one or more channels.\n');
0054    resp=input('Do you want to proceed (Y or N)? ','s');
0055    if strcmpi(resp,'n') || strcmpi(resp,'N'),
0056        fprintf('Call rm_chan.m aborted. EEG variable not modified.\n');
0057        return
0058    end
0059 end
0060 
0061 n_rmv=length(chan_names);
0062 rmv_ids=zeros(1,n_rmv);
0063 for r=1:n_rmv,
0064     n_chan=EEG.nbchan;
0065     %find channel ID#
0066     for c=1:n_chan,
0067         if strcmpi(EEG.chanlocs(c).labels,chan_names{r}),
0068             rmv_ids(r)=c;
0069         end
0070     end
0071     if ~rmv_ids(r),
0072         error('Could not find a channel with the name %s in this EEG variable.',chan_names{r});
0073     end
0074 end
0075 use_chans=setdiff(1:n_chan,rmv_ids);
0076 
0077 %remove channel from data & chanlocs
0078 EEG.data=EEG.data(use_chans,:,:);
0079 EEG.chanlocs=EEG.chanlocs(use_chans);
0080 EEG.nbchan=EEG.nbchan-n_rmv;
0081 
0082 %remove channel from calpulse info (MATLABmk fields)
0083 if ismember('cal_info',fldnms),
0084     EEG.cal_info.erps=EEG.cal_info.erps(use_chans,:);
0085     EEG.cal_info.usedcal_itemnum=EEG.cal_info.usedcal_itemnum(use_chans,:);
0086 end
0087 
0088 %get rid of EEGLAB ICA info
0089 EEG.icaact=[];
0090 EEG.icawinv=[];
0091 EEG.icasphere=[];
0092 EEG.icaweights=[];
0093 EEG.icachansind=[];
0094 EEG.chaninfo.icachansind=[];
0095 
0096 %get rid of MATLABmk ICA info
0097 if ismember('icfeatures',fldnms),
0098     EEG.icfeatures=[];
0099     EEG.icfreqs=[];
0100     EEG.iclabels=[];
0101     EEG.icspectra=[];
0102 end