Finding the frequency and the phase shift of a Sin signal

Use the findpeaks function on the absolute value of the first half of the complex Fourier transform to determine the index (preferably), then use that index to retuen the appropriate phase using the angle function on that value of the complex Fourier transform vector.

Something like this —

t = ...;                                                                    % Time Vector
s = ...;                                                                    % Signal Vector
Ts = mean(diff(t));                                                         % Sampling Interval (Assumed To Be Constant)
Fs = 1/Ts;                                                                  % Sampling Frequency
Fn = Fs/2;                                                                  % Nyquiat Frequency
FTs = fft(s - mean(s));                                                     % Fourier Transform
Fv = linspace(0, 1, fix(numel(t)/2+1)*Fn;                                   % Frequency Vector
Iv = 1:numel(Fv);                                                           % Index Vector
[pks, locs] = findpeaks(abs(FTs(Iv)));                                      % Peaks & Indices (May require'MinPeakHeight' Or 'MinPeakProminence' For Best Results)
Phase = angle(FTs(locs))                                                    % Phase Angle At Peak
PeakFreq = Fv(locs)

It may be necessary to experiment with this to get the result you want.

Ahmad Badran 2021-5-17

在 MATLAB Online 中打开

Thank you very much i set the number number of peaks to one and i think i got the wanted results

[pks, locs] = findpeaks(abs(FTs(Iv)),"NPeaks",1);                                      % Peaks & Indices (May require'MinPeakHeight' Or 'MinPeakProminence' For Best Results)
Phase = angle(FTs(locs));                                                 % Phase Angle At Peak
Phase0 = rad2deg(Phase)
PeakFreq = Fv(locs)

hope it's right

thank you again