%%%%%%%%%求極大值，極小值，并取包絡
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%
clear all;
close all
[FileName,PathName]=uigetfile('*.*');
lujing=[PathName,FileName];%輸入數據文件名路徑：'路徑'
shuju=dlmread(lujing);%讀取數據

a=shuju(:,2);

%求極大值
b=[1:1]*a(1);
num=[1:1]*1;
j=1+1;
mark=0;

for i=2:length(a)-1
    if (a(i)>a(i-1)&a(i)>a(i+1))
        b(j)=a(i);
        num(j)=i;
        mark=1;
    end
    if mark==1
        j=j+1;
    end
    mark=0;
end


%求極小值
b2=[1:1]*a(1);
num2=[1:1]*1;
j=1+1;
mark=0;

for i=2:length(a)-1
    if (a(i)<a(i-1)&a(i)<a(i+1))
        b2(j)=a(i);
        num2(j)=i;
        mark=1;
    end
    if mark==1
        j=j+1;
    end
    mark=0;
end
% %原始數據
% plot(shuju);hold on;
% %極大值數據
% plot(num,b);hold on;
% %極小值數據
% plot(num2,b2);hold on
% 
% figure

cc=fit(num',b','spline');%擬合
plot(cc);hold on
cc2=fit(num2',b2','spline');
aaa=plot(cc2);hold on
plot(shuju)