function [data_diff] = difference(data)
%差分編碼
%**************************************************************************
%data           輸入信號
%data_diff      差分編碼后信號
%**************************************************************************

%--------------------------------------------------------------------------
data_diff = zeros(1,length(data));
data_diff(1) = 1 * data(1);   %1為差分編碼的初始參考值
for i = 2:length(data)
    data_diff(i) = data_diff(i-1) * data(i);
end
%**************************************************************************