峰值检测代码 [英] Code for peak detection

问题描述

我想在第一步中计算实时信号是否通过某些阈值.第一步，我想检测真实信号是否在这些阈值以下通过(以便检测信号中的峰值).我的Matlab代码:

I want to calculate if a real-time signal pass some thresholds in the first step. In the first step, I want to detect if the real signal pass under those thresholds (in order to detect a peak in the signal). My Matlab code:

k=1;  
t = 1;
l=1;

for i =1:length(sm) //sm my signal.

    if (sm(i) > 0.25)
        first(k) = i;
        k = k+1;
        if (sm(i) > 0.5)

            second(t) = i;
            t =t +1;
            if (sm(i) > 0.75)

                third(l) = i;
                l = l+1;
            end
        end
    end
end

示例:

！[在此处输入图片描述] [1]

![enter image description here][1]

我想计算信号通过和低于三个阈值0.25，0.5，0.75的时间，并返回这些窗口.基本上，我的示例中有三个主要高峰.

I want to calculate the times that the signal pass over and under the three thresholds 0.25, 0.5, 0.75 and to return those windows. Basically the three main peaks that I have in my example.

基本上我想做的是使用fastsmooth函数和findpeaks.

Basically what am I trying to do is to use fastsmooth function and findpeaks.

signalSmoothed = fastsmooth(sm,50); plot(signalSmoothed)
[max_pk1 max_pk2] = findpeaks(signalSmoothed);
find(max_pk1 >0.5)
inversex = 1.01*max(signalSmoothed) - signalSmoothed;
[min_pk1 min_pk2]  = findpeaks(inversex);
find(min_pk1 >0.5) 

哪种启发式方法仅采用所需的峰值?此外，污损图像是离线示例.通常，我想在线执行该技术.

Which are the heuristics in order to take only the desired peaks? Moreover the depticted image is an offline example. Generally I want to perform the technique online.

我错误地将期望的曲线结果定义为峰值，这是整个波形而不仅仅是最大值.

I wrongfully defined as peak my desired curve result which is the whole wave not just the max value.

推荐答案

这里是一种解决方法，用于获取信号sm通过阈值 0.25 ， 0.50 和 0.75 .这些点可以转换为数据范围内的窗口，并存储在W中.最后，我们可以轻松地在同一图中绘制它们.请注意，我们需要在本地函数getwindows中进行一些检查以处理特殊情况，例如，当窗口在数据范围之外启动时.在另一个窗口中的窗口的检测是通过getwindowsspecial函数完成的.

Here is a solution to get the points where the signal sm passes the thresholds 0.25, 0.50 and 0.75. The points can be converted into windows inside the data-range and get stored in W. Finally we can plot them easily in the same figure. Note that we need to do some checks in the local function getwindows to handle special cases, for example when the window starts outside the data-range. The detection of windows inside another window is done in the getwindowsspecial-function.

这是代码:

function peakwindow
% generate sample data
rng(7);
sm = 2*rand(1,25)-0.5;
sm = interp1(1:length(sm),sm,1:0.01:100*length(sm));

% get points
firstup    = find(diff(sm > 0.25)==1);
secondup   = find(diff(sm > 0.50)==1);
thirdup    = find(diff(sm > 0.75)==1);
firstdown  = find(diff(sm < 0.25)==1);
seconddown = find(diff(sm < 0.50)==1);
thirddown  = find(diff(sm < 0.75)==1);

% plot the result
figure; hold on;
plot(sm,'k')
plot(firstup,sm(firstup),'*')
plot(firstdown,sm(firstdown),'*')
plot(secondup,sm(secondup),'*')
plot(seconddown,sm(seconddown),'*')
plot(thirdup,sm(thirdup),'*')
plot(thirddown,sm(thirddown),'*')

% get windows
W1 = getwindows(firstup,firstdown);
W2 = getwindows(secondup,seconddown);
W3 = getwindows(thirdup,thirddown);

% get special window
WS = getwindowsspecial(W1,W3);

% plot windows
plotwindow(W1,0.25,'r');
plotwindow(W2,0.50,'r');
plotwindow(W3,0.75,'r');
plotwindow(WS,0,'b-');


function W = getwindows(up,down)
if length(up)>1 && length(down)>1 && up(1)>down(1)
    down(1)=[]; % handle case when window begins out of bounds left
end
if length(up)<1 || length(down)<1;
    W = []; % handle if no complete window present
else
    % concatenate and handle case when a window ends out of bounds right
    W = [up(1:length(down));down]';
end


function plotwindow(W,y,lspec)
for i = 1:size(W,1)
    plot(W(i,:),[y,y],lspec)
end


% get windows of U where there is a window of H inside
function W = getwindowsspecial(U,H)
W = []; % empty matrix to begin with
for i = 1:size(U,1) % for all windows in U
    if any(H(:,1)>=U(i,1) & H(:,1)<=U(i,2))
        W = [W;U(i,:)]; % add window
    end
end

这是结果:

要查看处理是否正常，我们可以在用rng(3)初始化时绘制结果:

To see that the handling works properly, we can plot the result when initialized with rng(3):

请注意， 0.25 和 0.50 的窗口将超出界限，因此在绘制的窗口中不存在.

Note that the window of 0.25 and 0.50 would start out of bounds left and therefore is not present in the plotted windows.

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