function?[updown]?=?envelope（xyinterpMethod）

%ENVELOPE?gets?the?data?of?upper?and?down?envelope?of?the?known?input?（xy）.
%
%???Input?parameters:
%????x???????????????the?abscissa?of?the?given?data
%????y???????????????the?ordinate?of?the?given?data
%????interpMethod????the?interpolation?method
%
%???Output?parameters:
%????up??????the?upper?envelope?which?has?the?same?length?as?x.
%????down????the?down?envelope?which?has?the?same?length?as?x.
%
%???See?also?DIFF?INTERP1

%???Designed?by:?Lei?Wang??11-Mar-2003.
%???Last?Revision:?21-Mar-2003.
%???Dept.?Mechanical?&?Aerospace?Engineering?NC?State?University.
%?$Revision:?1.1?$??$Date:?3/21/2003?10:33?AM?$

if?length（x）?~=?length（y）
????error（‘Two?input?data?should?have?the?same?length.‘）;
end

if?（nargin??3）
error（‘Please?see?help?for?INPUT?DATA.‘）;
elseif?（nargin?==?2）
????interpMethod?=?‘linear‘;
end

%?Find?the?extreme?maxim?values?
%?and?the?corresponding?indexes
%----------------------------------------------------
extrMaxValue?=?y（find（diff（sign（diff（y）））==-2）+1）;
extrMaxIndex?=???find（diff（sign（diff（y）））==-2）+1;

%?Find?the?extreme?minim?values?
%?and?the?corresponding?indexes
%----------------------------------------------------
extrMinValue?=?y（find（diff（sign（diff（y）））==+2）+1）;
extrMinIndex?=???find（diff（sign（diff（y）））==+2）+1;

up?=?extrMaxValue;
up_x?=?x（extrMaxIndex）;

down?=?extrMinValue;
down_x?=?x（extrMinIndex）;

%?Interpolation?of?the?upper/down?envelope?data
%----------------------------------------------------
up?=?interp1（up_xupxinterpMethod）;?
down?=?interp1（down_xdownxinterpMethod）;

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

?????文件????????331??2016-02-19?12:16??Envelope_baoluo.m

?????文件???????1682??2016-01-28?13:57??envelope.m

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

?????????????????2013????????????????????2