How to find the average peak values and plot?

Question

Sohel Rana 2020-12-2

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https://ww2.mathworks.cn/matlabcentral/answers/674263-how-to-find-the-average-peak-values-and-plot

评论： Star Strider 2020-12-2

Hi,

I got the attached plot from the code below. I would like to start the graph from 0.3 instead of 0 (y-axis) and then do the average of peaks. Average peaks should be like: average of first and second peak, then average of second and third peak and so on. Then plot them like the attached figure but with the average peak values. I would really apprecite if someone help me with that?

m=1000;

I1=0.5;

I2=0.3;

I3=0.2;

L1=70*m;

L2=140*m;

n1=2;

n2=1.444;

index=n2;

lam=m*(1.5:0.000001:1.6);

Q12=(4*pi*n1*L1)./lam;

Q23=(4*pi*n2*L2)./lam;

Q13=Q12+Q23;

I=I1+I2+I3+2*sqrt(I1*I2).*cos(Q12)+2*sqrt(I2*I3).*cos(Q23)+2*sqrt(I1*I3).*cos(Q13);

plot(lam,I);

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Answer 1

Star Strider 2020-12-2

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/674263-how-to-find-the-average-peak-values-and-plot#answer_563153

在 MATLAB Online 中打开

Try this:

m=1000;
I1=0.5;
I2=0.3;
I3=0.2;
L1=70*m;
L2=140*m;
n1=2;
n2=1.444;
index=n2;
lam=m*(1.5:0.000001:1.6);
Q12=(4*pi*n1*L1)./lam;
Q23=(4*pi*n2*L2)./lam;
Q13=Q12+Q23;
I=I1+I2+I3+2*sqrt(I1*I2).*cos(Q12)+2*sqrt(I2*I3).*cos(Q23)+2*sqrt(I1*I3).*cos(Q13);
I = I + 0.3;
[pks, locs] = findpeaks(I);
pks_avg_2 = movmean(pks,2, 'Endpoints','discard');                  % Means Of Consecutive Points With Full Windows (Averaging Two Peaks) Only
figure
plot(lam,I)
hold on
stairs(lam(locs(1:numel(pks_avg_2))), pks_avg_2, '-r')
hold off
grid
legend('Data', 'Mean Of Two Consecuitve Peaks', 'Location','S')

.

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Sohel Rana 2020-12-2

Thank you for your quik response. I wanted to say I don't want to consider the values below 0.3 (or 0.5) from my original plot for any further analysis. Think my original plot starts from 0.5 as below (cut the graphs below 0.5). Can I get sine wave like graph (see in thin black line) instead of stair like? Can I get envelope of this graph which will look like sine wave?

Star Strider 2020-12-2

在 MATLAB Online 中打开

I have absolutely no idea what you want.

Try this:

m=1000;
I1=0.5;
I2=0.3;
I3=0.2;
L1=70*m;
L2=140*m;
n1=2;
n2=1.444;
index=n2;
lam=m*(1.5:0.000001:1.6);
Q12=(4*pi*n1*L1)./lam;
Q23=(4*pi*n2*L2)./lam;
Q13=Q12+Q23;
I=I1+I2+I3+2*sqrt(I1*I2).*cos(Q12)+2*sqrt(I2*I3).*cos(Q23)+2*sqrt(I1*I3).*cos(Q13);
I = I + 0.3;
[pks1, locs1] = findpeaks(I, 'MinPeakHeight',2);                        % Peaks >= 2.0
[pks2, locs2] = findpeaks(I, 'MinPeakHeight',0.5);                      % Peaks >= 0.5
pks_avg_2 = movmean(pks2,2, 'Endpoints','discard');                     % Means Of Consecutive Points With Full Windows (Averaging Two Peaks) Only
figure
plot(lam,I)
hold on
plot(lam(locs2(1:numel(pks_avg_2))), pks_avg_2, '-r')
plot(lam(locs1), pks1, '-k')
hold off
grid
legend('Data', 'Mean Of Two Consecuitve Peaks', 'Selected Peak Amplitudes (>=2)', 'Location','S')