MATLAB 中的波峰和波谷（但有相应的波峰和波谷定义）

Question

我想在给定的数据向量中寻找波峰和波谷，定义如下。

“峰”是比前一个波谷至少高 x% 的局部最大值，而“波谷”是比前一个波峰低至少 x% 的局部最小值。这里的 x 称为截止值。在我写的论文中，cutoff 被称为数据的标准差。

我想写一个函数来让我找到一个高峰和一个低谷。我写的函数就是这个。我将从主要数据中调用它。

function [vectpeak,vecttrough]=peaktrough(cutoff,x,lastobs,t)

% This function gives you two outputs: a vector of ones and zeros that locate PEAKS and     
% a vector of ones and zeros that locate TROUGHS. 
% To be able to get a vector of peaks and troughs, we have to give 
% four inputs.
% CUTOFF: This is what Chang and Osler [1999] use to identify if a data
% point is a peak or a trough. A PEAK is defined as "a local maximum that is
% x percent higher than the preceding trough." (Chang and Osler, 1999) 
% and a TROUGH is defined as "a local minimum that is x percent lower 
% than the preceding peak." This is a scalar.
% VECTOR: This is the vector of data that will be used for the purposes of
% the identification.
% LASTOBS: This is the last observation of the data.
% t: This specifies the time.

% Pre-allocations.
vectpeak=zeros(lastobs,1); % This is the vector of peaks.
vecttrough=zeros(lastobs,1); % This is the vector of troughs.

% Computing for the troughid's and peakid's.
temptroughid=troughid(cutoff,x,lastobs,t);
temppeakid=peakid(cutoff,x,lastobs,t);

 % Determining whether a function is a peak or a trough.
 while t<lastobs
    t=t+1;
    if x(t)>=temptroughid(t);
        vecttrough(t)=1;
        vectpeak(t)=0;
        maximum=x(t);
    elseif x(t)<=temppeakid(t);
            vecttrough(t)=0;
            vectpeak(t)=1;
            minimum=x(t);
    else
            vecttrough(t)=0;
            vectpeak(t)=0;
    end
end

function findtrough=troughid(cutoff,y,lastobs,t)
% This function computes for the TROUGHID which will be used in
% determining whether we have a trough or a peak.

% Initializations. 
findtrough=zeros(lastobs,1);
tempmin=zeros(lastobs,1);
minimum=y(1);

% This is how the function works.
while t<lastobs;
    t=t+1;
    if y(t)<minimum;
       tempmin(t)=y(t);
       minimum=y(t);
    else tempmin(t)=minimum;
    end
    findtrough(t)=tempmin(t)*(1+cutoff);
end
end

function findpeak=peakid(cutoff,y,lastobs,t)
% This function computes for the PEAKID which will be used in
% determining whether we have a peak.

% Initializations.
findpeak=zeros(lastobs,1);
tempmax=zeros(lastobs,1);
maximum=y(1);

% This is how the function works.
while t<lastobs;
     t=t+1;
     if y(t)>maximum;
       tempmax(t)=y(t);
       maximum=y(t);
    else tempmax(t)=maximum;
    end
    findpeak(t)=tempmax(t)*(1-cutoff);
end
end
end

我遇到的问题是我得到了奇怪的结果。例如，我得到一个向量，其中所有的都是波峰，没有波谷，这是没有意义的，因为如果我使用 MATLAB 的 findpeaks 命令，我能够识别波峰和波谷，它们不是连续的。

有没有一种方法可以调整我的代码，或者如果没有，可以使用 findpeaks 或其算法根据我的定义找到峰值和谷值？

Answer 1

事实上，您的代码实际上并不能识别波峰或波谷。我认为您可能应该从 findpeaks 开始获取候选峰和谷的列表。然后，逐步浏览此列表以测试是否每个都满足条件。