--- a
+++ b/functions/@memmapdata/sum.m
@@ -0,0 +1,75 @@
+% SUM - sum of memory mapped underlying array
+%
+% Author: Arnaud Delorme, SCCN, INC, UCSD, Nov. 2008
+
+% Copyright (C) 2008 Arnaud Delorme, SCCN, INC, UCSD
+%
+% This file is part of EEGLAB, see http://www.eeglab.org
+% for the documentation and details.
+%
+% Redistribution and use in source and binary forms, with or without
+% modification, are permitted provided that the following conditions are met:
+%
+% 1. Redistributions of source code must retain the above copyright notice,
+% this list of conditions and the following disclaimer.
+%
+% 2. Redistributions in binary form must reproduce the above copyright notice,
+% this list of conditions and the following disclaimer in the documentation
+% and/or other materials provided with the distribution.
+%
+% THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+% AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+% IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+% ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+% LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+% CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+% SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+% INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+% CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+% ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
+% THE POSSIBILITY OF SUCH DAMAGE.
+
+function [s] = sum(a,dim)
+    
+    if nargin < 2
+        dim = 1;
+    end
+    
+    %b = (:,:,:);
+    if ~strcmpi(a.fileformat, 'transposed')
+        s = sum(a.data.data.x, dim);
+    else
+        alldim = [3 1 2];
+        if length(size(a)) == 3
+            dim = alldim(dim);
+            s = sum(a.data.data.x, dim);
+            s = permute(s, [3 1 2]);
+        else
+            if dim == 1
+                 dim = 2;
+            else dim = 1;
+            end
+            s = sum(a.data.data.x, dim)';
+        end
+    end
+    return;
+    
+    % do pnts by pnts if dim = 1
+%     if dim == 1 & length(
+%         
+%         s = zeros(size(a,2), size(a,3));
+%         for i=1:size(a,2)
+%             s(i,:) = mean(a.data.data.x(:,i,:));
+%         end
+%     elseif dim == 1
+%          s = zeros(size(a,1), size(a,1));
+%         for i=1:size(a,1)
+%             s(i,:) = mean(a.data.data.x(:,:,:));
+%         end
+%        
+%         
+%     s = builtin('sum', rand(10,10), dim);
+    
+    %if length(size(a)) > 2
+    %else s = sum(a(:,:,:), dim);
+    %end