function?apen?=?Fuzzy_entropy_bbd（nrt）
%%?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/
%%用相關系數來度量r
load?xa;
data?=xa（1:600）;

%?尺度因子
?t=20;



Mmm=fix（length（data）/t）;
for?i=1:Mmm
???????Yn（i）=?sum?（?data（（（（i-1）*t）+1）?:（i*t）?）?）/?t?