# Get the position, period and the amplitud of the wave.

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Vicente il 24 Apr 2023
As I wrote in the title I have a wave and I want to get the period of it, the amplitud and the top peack of it. I already got a code that I tried but it does not work to me, do not know why. I upload the matlab data simplify the task. Thank you in advance!
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Antoni Garcia-Herreros il 24 Apr 2023
Modificato: Antoni Garcia-Herreros il 24 Apr 2023
Hello Vicente,
You can try a couple of different approaches:
Option A: Use findpeaks function to get the values of the peaks and compute the differences to obtain the amplitude and the period.
x=Tm(4000:5000);
y=P01m(4000:5000);
[Mpy,Mpx]=findpeaks(y); % Find local maximums
[mpy,mpx]=findpeaks(-y);% Find local minimums
T=mean(diff(x(Mpx))); % Period
A=mean(y(Mpx)-y(mpx(1:end-1)))*0.5; %Amplitude
toppeak=mean(Mpy); %Max peak value
Option B: Fit your data into a sinusoidal and use the parameters to obtain the desired values
fitfun = fittype( @(a,b,x) a*sin(b*x+c)); % Define the sinusoidal
[fitted_curve] = fit(x,y,fitfun,'StartPoint',[5.3,6.97,-7.6])
plot(x,y,'.') %Plot the model to ensure the fit works
hold on
plot(x,fitted_curve(x))
A=fitted_curve.a; % Amplitude of your wave
T=2*pi/fitted_curve.b; % Period = 2pi/f
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Vicente il 24 Apr 2023
Hi, thank you for the options, could you tell me which variable is fpx in the first option, it causes error in the code.
Antoni Garcia-Herreros il 24 Apr 2023
Sorry, it was a typo, I just eddited the code

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