second largest peak value

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Ramesh Bala 2019-6-12

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/466643-second-largest-peak-value

评论： Ramesh Bala 2019-8-6

采纳的回答： Alex Mcaulley

I'm getting the amp of second largest peak as correct but the time is wrong ?

How to obtain the second highest value X,Y from this and plot as already Y is correct ,X seems to be in wrong region?

s=load ('30827.mat');

signal(1,1:length(s.ans))=s.ans;

load t.mat;

[PkAmp, PkTime] = findpeaks(abs(hilbert(signal(1,:))),t);

[highestPeak, indexOfHighestPeak] = max(PkAmp);

[a(1),b2]=max(abs(hilbert(signal(1,:))));

[a2(1),b6]=max(PkAmp(PkAmp<max(PkAmp))); % to get second largest peak value

% error is the time value calcluate and plotted wrong??

Highesttime(1,:) = t(b2);

Highest2time(1,:) = t(b6);

figure;

plot(t,(signal(1,:)),t,abs(hilbert(signal(1,:))),t(b2),a(1),'ro')

hold on

plot(PkTime, PkAmp, '^r', 'MarkerFaceColor','r')

xlim([0 0.0006]);ylim([-inf inf])

grid on

hold on,plot(t(b6),a2(1),'ko')

hold off

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采纳的回答

Alex Mcaulley 2019-6-12

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/466643-second-largest-peak-value#answer_378827

在 MATLAB Online 中打开

To obtain the coordinates of the second peak you just need:

[PkAmp, PkTime] = findpeaks(abs(hilbert(signal(1,:))),t); 
[~,idx] = sort(PkAmp,'descend');
PkAmp(idx(2)) %Amplitude of the second peak
PkTime(idx(2)) %Time of the second peak

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Ramesh Bala 2019-8-6

Dear Alex

I have one more silly doubt in removing the index,I'm trying to find now the the largest time instead of Amp.So,I have used 'ascend' function which helps me to plot the the required time.

clc

clear all

close all

format long;

filenames={"30827"}

S(:,1) = [25 25 21.4 17.92 28.5 32.07 30 35 20 15];

S(:,2)= [10 15 8.5 12.07 8.5 12.07 5 5 5 5 ];

for i=1:numel(filenames)

s(i)=load (filenames{i});

signal(i,1:length(s(i).ans))=s(i).ans; % loading the signals from the scanning pts

end

load t.mat; %loading the time values

for k=1:1:length(S)

[a(k),b2]=max(abs(hilbert(signal(k,:)))); % first peak amp & index

%finding the peaks

set(0,'DefaultFigureWindowStyle','docked')

[PkAmp, PkTime] = findpeaks(abs(hilbert(signal(k,:))),t);

[~,idx] = sort (PkTime, 'ascend' );

b6(k) = idx(4); % Index of the fourth largest peak

a6(k) = PkAmp(b6(k)); % Amplitude of the fourth largest peak

time4(k)= PkTime (b6(k)); % Time of the fourth largest peak

figure;

plot(t,(signal(k,:)),t,abs(hilbert(signal(k,:))),t(b2),a(k),'ro')

hold on;grid on

plot(PkTime, PkAmp, '^r', 'MarkerFaceColor','r')

%plotting 4th largest

hold on,plot(time4(k), a6(k),'ko')

hold off

end

As per the script it plots the 4th largest PKTime peak .But how to remove other PkTime based on highest "a" highest PKAmp and then recontinue to plot the graph by taking highest(PKAMP) as PKTIME 1?

Ramesh Bala 2019-8-6