Question

我想在给定的数据向量中查找峰值和低谷，具有以下定义。

“峰值”是局部最大值，比前一个谷值高至少x％，“谷值”是局部最小值，比前一个峰值低至少x％。这里的x被称为截止。在我写的论文中，截止值被称为数据的标准差。

我想写一个功能，让我找到一个高峰和一个低谷。我写的功能就是这个。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

我得到的问题是我得到了奇怪的结果。例如，我得到一个矢量，其中所有都是峰值，没有一个是低谷，这没有意义，因为如果我使用MATLAB的findpeaks命令，我能够识别峰值和谷值，它们不是连续。

有没有办法我可以调整我的代码，或者如果没有，使用findpeaks或其算法根据我的定义找到峰值和低谷？

Answer 1

实际上，您的代码实际上并未识别峰值或波谷。我认为你应该从findpeaks开始，以获得候选峰值和低谷的列表。然后，逐步执行此列表以测试每个是否满足条件。

MATLAB中的峰值和谷值（但具有峰值和谷值的相应定义）

1 个答案: