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

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];

Answer 1

[Voss]

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

[MANINDER CHOUDHARY]

Thank you for your asnswer. Actually, I'm trying to find something else. The figure you posted has positive and negative peak and according to your code it takes all peaks (pos or neg), sort them and store into variable. My object is to get only first peak of each pulse whether positive or negative. If you look at the figure the pulse has positive and negative peak, but first peak is negative ( red circle) so I want to take only negative value into account and want to omit postive value as its on second palce. After sometime another pulse will appear and similary the positve and negative peaks will appear but i want to consider only first peak. whether its positve or negative.

Hope I was able to express the problem

[Voss]

Sounds like you have to define mathematically what a pulse is, i.e., how to distinguish between one pulse and another pulse. Maybe each pulse has two peaks, maybe not.

[MANINDER CHOUDHARY]

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]

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