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

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!

Answer 1

[Antoni Garcia-Herreros]

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

[Vicente]

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]

Sorry, it was a typo, I just eddited the code