--- a
+++ b/functions/@mmo/sum.m
@@ -0,0 +1,47 @@
+% 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 sumval = sum(obj,dim)
+    
+    if nargin < 2
+        dim = 1;
+    end
+    
+    s1  = size(obj);
+    ss.type = '()';
+    ss.subs(1:length(s1)) = { ':' };
+    for index = 1:s1(dim)
+        ss.subs{dim} = index;
+        if index == 1
+             sumval = subsref(obj, ss);
+        else sumval = sumval + subsref(obj, ss);
+        end
+    end