keypoint.m

自己编写的实现时间序列中的关建点搜索

function [keyda1]=keypoint(data,K,t)
%function [ keyda1,keyda2,keydata ] = keypoint( data,m,n,t)
%UNTITLED1 Summary of this function goes here
%  Detailed explanation goes here
%keyda1 存储夹角方法取得的关键点
%keyda2 存储幅值方法取得的关键点
%data is the time series data which you want to search key point
%m is the threshold value of angle
%n is the threshold value of amplitude
%t is the time per sample-rate

keyda1(1)=data(1);
[d,n]=size(data);

j=2;
for i=2:n-1
   %求斜率
   a=[data(i)-data(i-1)]/t;
   b=[data(i)-data(i+1)]/t;
   if a*b==1
       e(i)=pi/2;
  
  else 
   c=(b-a)/(1-a*b);
   e(i)=atan(c);    %计算出的夹角  
end
end

[f,ind]=sort(e)  %夹角排序

  s=1;
  for j=2:K+1
      keyda1(j)=data(ind(s));
      s=s+1;
  end