Area between the peak of the signal

Hi,

Anyone know how to calculate for the area of torque between the peak (triangle label) of the signal?

Can anyone please help me?

Thank you.

[Mathieu NOE]

hello

sorry , it's not clear to me how you define the area ? you want to do some integration of your signal between two successive peaks ?

[Yew Jen Chong]

Hi, I want to find the area between the triangle labels which has number above. Is it possible to find the area between them?

[Star Strider]

How did you identify those specific peaks?

I am having problems reproducing that with findpeaks.

[Yew Jen Chong]

Hi, since the time in x-axis increase constantly, therefore the time in the second row will be selected to convert into frequency as the first row is zero. The frequency will be used in the findpeaks with minimum peak distance, minimum peak prominence, and minimum peak height is included to produce the graph above.

The code below is for producing the graph

findpeaks(cm.Torque_Nm_,Fs,'MinPeakDistance',0.016,'MinPeakProminence',5,'MinPeakHeight',6);

The code below is for storing information

[pksRT_after,locsRT_after] = findpeaks(cm.Torque_Nm_,Fs,'MinPeakDistance',0.016,'MinPeakProminence',5,'MinPeakHeight',6);

I hope I answer your question

Answer 1

[Star Strider]

I had to tweak the code slightly to get the result I needed for the ‘areav’ and ‘absareav’ calculations.

Try this —

% opts = weboptions('ContentType','text');
% W = webread('https://www.mathworks.com/matlabcentral/answers/uploaded_files/1035225/s.m', opts)

T1 = readtable('https://www.mathworks.com/matlabcentral/answers/uploaded_files/1035230/signal.csv', 'VariableNamingRule','preserve');

t = T1.('Time [s]');
Fs = 1/t(2);
Torque = T1.('Torque [Nm]');
env = envelope(Torque, 100, 'peak');
Lv = env >= 5;
LastIdx = find(Lv,1,'last');

[pksRT_after,locsRT_after] = findpeaks(Torque,'MinPeakDistance',100,'MinPeakProminence',20,'MinPeakHeight',6);
locsRT_afterv = [locsRT_after; LastIdx];

for k = 1:numel(locsRT_afterv)-1
    idxrng = locsRT_afterv(k) : locsRT_afterv(k+1);
    t_midrng(k) = median(t(idxrng));                            % Used In 'text' Call
    areav(k) = trapz(t(idxrng),Torque(idxrng));                 % Area
    absareav(k) = trapz(t(idxrng),abs(Torque(idxrng)));         % Absolute Area
end

% buffer(areav,10)
% buffer(absareav,10)

figure
plot(t(Lv), Torque(Lv))
grid
hold on
plot(t(locsRT_after), pksRT_after, '^r')
% plot(t, env, '-r')
hold off
text(t_midrng, pksRT_after/2, compose('   \\leftarrow Area = %.4f',areav), 'Horiz','left', 'Vert','middle', 'Rotation',90, 'FontSize',9)

The loop uses trapz to calculate the areas between the locations denoted by the red triangles. The code then plots and labels them. (It uses the envelope function to define the area of interest in the signal for the plot.)

.

[Yew Jen Chong]

@Star Strider Thank you for your helping.

[Star Strider]

As always, my pleasure!