function result = operation(oper,data1,data2)

 result = [];

if length(data1) ~= length(data2)
    return
end

l      = length(data1;
result = ones(l,1) * NaN;
switch (oper)
    case '+'
        for n = 1 : l
            if ~isnan(data1(n)) && ~isnan(data2(n))
                result(n) = data1(n) + data2(n);
            elseif ~isnan(data1(n)) && isnan(data2(n))
            elseif ~isnan(data1(n)) && isnan(data2(n))
            end
        end
    case '-'
end


end