How to extract only first peak of each pulse (positive or negative) in sequence throughout the signal

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MANINDER CHOUDHARY 2022-5-25

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https://ww2.mathworks.cn/matlabcentral/answers/1726660-how-to-extract-only-first-peak-of-each-pulse-positive-or-negative-in-sequence-throughout-the-sign

评论： Voss 2022-5-27

Example.mat

I would like to extract only first value of the peak, whether its positive or negative in a sequence and store in a array

My code is

data = C;

t = 1:length(data);

figure

plot(t,data)

xlabel('original data');

ylabel('amp')

legend('Noisy data Signal')

grid on

[p,s,mu] = polyfit((1:numel(data))',data,1);

fn = polyval(p,(1:numel(data))',[],mu);

x_data = data - fn;

[~,locs_Rwave] = findpeaks(x_data,'MinPeakHeight',0.005,'MinPeakDistance',3000);

inv = -x_data;[~,locs_Swave] = findpeaks(inv,'MinPeakHeight',0.005,'MinPeakDistance',3000);

[m_Peak, locs_m_peak] = findpeaks(abs(x_data),'MinPeakHeight',0.005,'MinPeakDistance',3000);

pos_pulses= [x_data(locs_Rwave),locs_Rwave];

neg_pulses= [x_data(locs_Swave),locs_Swave];

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Answer 1

Voss 2022-5-25

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1726660-how-to-extract-only-first-peak-of-each-pulse-positive-or-negative-in-sequence-throughout-the-sign#answer_971495

在 MATLAB Online 中打开

Example.mat

load Example.mat

data = C;

t = 1:length(data);

[p,s,mu] = polyfit((1:numel(data))',data,1);

fn = polyval(p,(1:numel(data))',[],mu);

x_data = data - fn;

[pks_Rwave,locs_Rwave] = findpeaks(x_data,'MinPeakHeight',0.005,'MinPeakDistance',3000);

[pks_Swave,locs_Swave] = findpeaks(-x_data,'MinPeakHeight',0.005,'MinPeakDistance',3000);

[peak_locations,sort_idx] = sort([locs_Rwave; locs_Swave]);

peak_values = [pks_Rwave; -pks_Swave];

peak_values = peak_values(sort_idx);

plot(x_data)

hold on

plot(peak_locations,peak_values,'ro')

xlim([2.992e5 2.996e5])

first_peak_location = peak_locations(1)

first_peak_location = 299266

first_peak_value = peak_values(1)

first_peak_value = -0.0122

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MANINDER CHOUDHARY 2022-5-27

There are two peaks i.e. positive and negative however the pulse starts with negative peak value (First peak), i just want to take first peak value and store it somwewhere, and then move ahead to second pulse and repeat the same procedure trhrougout . Hope now its clear

Voss 2022-5-27

在 MATLAB Online 中打开

I think I understand now. You want to know the location and/or value of the first peak of each pulse, under the assumption that each pulse has two peaks.

The code I showed has all the peak locations sorted, so, since each pulse has two peaks and you want the first peak of each pulse, you can simply take every alternate peak, starting with the first peak:

peak_locations(1:2:end) % location of the first peak of each pulse
peak_values(1:2:end) % value or height of the first peak of each pulse

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