function?[apen]?=?approx_entropy_bbd（nra）
%%?Code?for?computing?approximate?entropy?for?a?time?series:?Approximate
%?Entropy?is?a?measure?of?complexity.?It?quantifies?the?unpredictability?of
%?fluctuations?in?a?time?series

%?To?run?this?function-?type:?approx_entropy（‘window?length‘‘similarity?measure‘‘data?set‘）

%?i.e??approx_entropy（50.5a）

%?window?length=?length?of?the?window?which?should?be?considered?in?each?iteration
%?similarity?measure?=?measure?of?distance?between?the?elements
%?data?set?=?data?vector

%?small?values?of?apen?（approx?entropy）?means?data?is?predictable?whereas
%?higher?values?mean?that?data?is?unpredictable

%?concept?boorowed?from?http://www.physionet.org/physiotools/ApEn/

%?Author:?Avinash?Parnandi?parnandi@usc.edu?http://robotics.usc.edu/~parnandi/



data?=a;


for?m=n:n+1;?%?run?it?twice?with?window?size?differing?by?1

set?=?0;
count?=?0;
counter?=?0;
window_correlation?=?zeros（1（length（data）-m+1））;

for?i=1:（length（data））-m+1
????current_window?=?data（i:i+m-1）;?%?current?window?stores?the?sequence?to?be?compared?with?other?sequences
????%%??計算兩個之間的差超過多少的個數
????for?j=1:length（data）-m+1
????sliding_window?=?data（j:j+m-1）;?%?get?a?window?for?comparision?with?the?current_window
????
????%?compare?two?windows?element?by?element
????%?can?also?use?some?kind?of?norm?measure;?that?will?perform?better
????for?k=1:m
????????if（（abs（current_window（k）-sliding_window（k））>r）?&&?set?==?0）
????????????set?=?1;?%?i.e.?the?difference?between?the?two?sequence?is?greater?than?the?given?value??只要有兩個的距離大于r就置為1
????????end
????end%k=1:m
????if（set==0）?
?????????count?=?count+1;?%?this?measures?how?many?sliding_windows?are?similar?to?the?current_window
????end
????set?=?0;?%?reseting?‘set‘
????
????end%j=1:length（data）-m+1?end結束后得到所有落在模板i的r內的個數
???counter（i）=log（count/（length（data）-m+1））;?%?we?need?the?number?of?similar?windows?for?every?cuurent_window
???count=0;
i;
end??%??for?i=1:（length（data））-m+1?ends?here


counter;??%?this?tells?how?many?similar?windows?are?present?for?each?window?of?length?m
%total_similar_windows?=?sum（counter）;

%window_correlation?=?counter/（length（data）-m+1）;
correlation（m-n+1）?=?（（sum（counter））/（length（data）-m+1））;


?end?%?for?m=n:n+1;?%?run?it?twice???
???correlation（1）;
???correlation（2）;
apen?=?correlation（1）-correlation（2）;
%?apen?=?log（correlation（1）/correlation（2））;

?屬性????????????大小?????日期????時間???名稱
-----------?---------??----------?-----??----

?????文件???????2417??2011-04-12?09:20??Entropy\approx_entropy_my.m

?????文件???????1737??2011-04-13?15:20??Entropy\Fuzzy_entropy_my.m

?????文件???????2019??2011-04-13?11:19??Entropy\Sample_entropy_my.m

?????文件???????1735??2017-12-14?11:43??Entropy\模糊熵.m

?????文件???????2610??2017-12-15?13:29??Entropy\相對熵.m

?????目錄??????????0??2018-05-04?10:31??Entropy

-----------?---------??----------?-----??----

????????????????10518????????????????????6