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subsref.m
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Wed, Feb 19, 12:27

subsref.m
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function varargout=subsref(this,subs)
% SUBSREF Subscripted reference
% An overloaded function...
% _________________________________________________________________________
% Copyright (C) 2008-2013 Wellcome Trust Centre for Neuroimaging
% Vladimir Litvak, Stefan Kiebel
% $Id: subsref.m 5710 2013-10-22 14:01:23Z guillaume $
if isempty(subs)
return;
end
if this.Nsamples == 0
error('Attempt to reference a field of an empty meeg object.');
end
switch subs(1).type
case '()'
if ~islinked(this), error('The object is not linked to data file'); end
if numel(subs)~= 1, error('Expression too complicated'); end
if this.montage.Mind==0
varargout = {double(subsref(this.data, subs))};
else
Mem_max = 200*2^20; % Limit memory usage to about 200Mb
vect_fl = 0; dat3D = 0;
dim = size(this);
if numel(dim)>2 && dim(3)>1
% assume at most 3D data
dat3D = 1;
end
if ischar(subs.subs{1})
% need to handle the case of a ':' argument
if ~strcmp(subs.subs{1},':'), error('This shouldn''t happen....'); end
if length(subs.subs) == 1
chanidx = 1:dim(1);
subs.subs{2} = ':';
if dat3D, subs.subs{3} = ':'; end
vect_fl = 1;
else
chanidx = 1:dim(1);
end
else
chanidx = subs.subs{1};
end
%check if correct channel index
if any(chanidx > nchannels(this))
error('channel index higher than number of channels in current montage')
end
% get corresponding rows of 'tra' matrix
traidx = this.montage.M(this.montage.Mind).tra(chanidx,:);
%change subs to use only the necessary channels from data
lchan_o = find(any(traidx,1));
subs.subs{1} = lchan_o;
if ischar(subs.subs{2})
if ~strcmp(subs.subs{2},':'), error('This shouldn''t happen....'); end
Ntb = dim(2);
else
Ntb = length(subs.subs{2});
end
if dat3D && ischar(subs.subs{3})
if ~strcmp(subs.subs{3},':'), error('This shouldn''t happen....'); end
subs.subs{3} = 1:dim(3);
end
Mem_load = 8*Ntb*length(lchan_o);
if Mem_load<=Mem_max % small chunk loaded
if dat3D
subs_c = subs;
for ii=1:numel(subs.subs{3})
subs_c.subs{3} = subs.subs{3}(ii);
varargout{1}(:,:,ii) = ...
traidx(:,lchan_o)*double(subsref(this.data, subs_c));
end
else
varargout = {traidx(:,lchan_o)*double(subsref(this.data, subs))};
end
else % otherwise split data reading into chunks
Ntb_chunk = round(Mem_max/length(lchan_o)/8);
Nchunk = ceil(Ntb/Ntb_chunk);
varargout{1} = zeros(length(chanidx),Ntb);
for ii=1:Nchunk
subs_ch = subs;
if ii<Nchunk
ll = (1:Ntb_chunk)+(ii-1)*Ntb_chunk;
else
ll = ((ii-1)*Ntb_chunk):Ntb;
end
subs_ch.subs{2} = ll;
if dat3D
for jj=1:numel(subs.subs{3})
subs_ch.subs{3} = subs.subs{3}(jj);
varargout{1}(:,ll,jj) = ...
traidx(:,lchan_o)*double(subsref(this.data, subs_ch));
end
else
varargout{1}(:,ll) = ...
traidx(:,lchan_o)*double(subsref(this.data, subs_ch));
end
end
end
if vect_fl, varargout{1} = varargout{1}(:); end
end
case '{}'
case '.'
if ismethod(this, subs(1).subs)
if numel(subs) == 1
varargout = {feval(subs(1).subs, this)};
elseif (numel(subs) == 2) && isequal(subs(2).type, '()')
varargout = {feval(subs(1).subs, this, subs(2).subs{:})};
elseif (numel(subs)> 2) && isequal(subs(2).type, '()')
varargout{1} = builtin('subsref', ...
feval(subs(1).subs, this, subs(2).subs{:}), subs(3:end));
else
varargout{1} = builtin('subsref', feval(subs(1).subs, this), subs(2:end));
end
elseif isfield(this.other, subs(1).subs)
field = getfield(this.other, subs(1).subs);
if numel(subs)==1
varargout = {field};
else
varargout{1} = builtin('subsref', field, subs(2:end));
end
else
error('Reference to non-existent or private meeg method or field.');
end
otherwise
error('Unfamiliar referencing type');
end

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