You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: std_chantopo.m
    path of file: ./repos/eeglab/functions/studyfunc
    
    the code of the file until where you have to start completion: % STD_CHANTOPO - plot ERP/spectral/ERSP topoplot at a specific
%                  latency/frequency. 
% Usage:
%          >> std_chantopo( data, 'key', 'val', ...)
% Inputs:
%  data  -  [cell array] mean data for each subject group and/or data
%           condition. These arrays are usually returned by function
%           std_erspplot and std_erpplot. For example
%
%           >> data = { [1x64x12] [1x64x12 }; % 2 groups of 12 subjects, 64 channels
%           >> std_chantopo(data, 'chanlocs', 'chanlocfile.txt');
%
% Scalp map plotting option (mandatory):
%  'chanlocs'    - [struct] channel location structure
%
% Other scalp map plottin
    
function cannot plot complex values'); end
                topoplot( tmpplot, opt.chanlocs, opt.topoplotopt{:});
                if isempty(opt.caxis)
                    tmpc = [ min(min(tmpplot), tmpc(1)) max(max(tmpplot), tmpc(2)) ];
                else 
                    caxis(opt.caxis);
                end
                title(opt.titles{c,g}, 'interpreter', 'none'); 
            else
                axis off;
            end
        else
            axis off;
        end

        % statistics across groups
        % -------------------------
        if strcmpi(opt.effect, 'marginal') || (strcmpi(opt.effect, 'main') && c == 1)
            if g == ng && ng > 1 && ~isempty(opt.groupstats)
                if strcmpi(opt.effect, 'main') && nc>1, centerc = nc/2-0.5; else centerc = 0; end
                hdl(c,g+1) = mysubplot(nc+addr, ng+addc, c+centerc, ng + 1, opt.transpose);
                pgroupplot{c}(pgroupplot{c} <0) = 0;
                topoplot( pgroupplot{c}, opt.chanlocs, opt.ptopoopt{:});
                title(opt.titles{c,g+1}, 'interpreter', 'none');
                caxis([-maxplot maxplot]);
            end