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Frequency, amplitude, phase and mean value of sine wave

Miroslav Balda (view profile)

13 May 2008 (Updated )

The function sinfapm evaluates parameters of sampled sine wave

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Description

The function sinfap.m evaluates frequency, amplitude, phase and mean value of a uniformly sampled harmonic signal
x(t) = a.sin(2.pi.f.t + phi) + x_m
It uses a vector version of 3-point formulae derived by application of
Z-transform (see [1]) for finding amplitude and frequency of a signal.
If more than two output parameters are to be determined, all of them are optimized in the least squares sense by the function LMFnlsq.

Calls:
frq = sinfapm(x,fs); % Get only frequaency of sine-wave
[frq,amp] = sinfapm(x,fs); % Get frequency and amplitude
[frq,amp,phi] = sinfapm(x,fs); % Get frequency, amplitude and phase
[frq,amp,phi,ave] = sinfapm(x,fs); % ditto plus mean value
The set of more than two output parameters can be found by calling
[frq,amp,phi] = sinfapm(x,fs,Name_1,Val_1,Name_2,Val_2, ...);
[frq,amp,phi,ave] = sinfapm(x,fs,Name_1,Val_1,Name_2,Val_2, ...);

Input arguments:
x % vector of samples
fs % sampling frequency [Hz]
Name_i % name of the i-th optional parameter for optimization
Val_i % value of the i-th optional parameter (see function LMFnlsq)
Output arguments:
frq % frequency of x [Hz]
amp % amplitude of x
Examples:
[f,a,phi,ave] = sinfapm([1.3633;-.2428;-0.9705;1.8130;-1.9631],10);
% f = 4.0000
% a = 2.0000
% phi = 0.7500
% ave = -2.2806e-005
[f,a,phi] = sinfapm([.707,1,.707,0],20,'Xtol',1e-4);
% f = 2.5001
% a = 0.9999
% phi = 0.7853 % pi/4 = 0.785398...

Acknowledgements

This file inspired Sinide Parameter Identification Of A Sine Wave From A Measured Signal.

MATLAB release MATLAB 7.6 (R2008a)
Other requirements Function LMFnlsq from FEX, Id. 17534
18 Aug 2014 Miroslav Balda

Miroslav Balda (view profile)

The function sinfapm is not maintained any more. Use the function sinide instead, which is much more stable. See

sinide: www.mathworks.com/matlabcentral/fileexchange/45567

Comment only
13 Mar 2014 will wehner

will wehner (view profile)

Thank you.
Unfortunately, I believe there are still problems with the function.

I emailed you an example (miroslav@balda.cz) with estimation of real data. It uses your function and compares to estimation with nlinfit.m

Will

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14 Feb 2014 Miroslav Balda

Miroslav Balda (view profile)

@Will
I am sorry that the function behaved wrong. A reason for it was a hight sensitivity of the function to inaccurate initial guess of the sought parameters. Since it was impossible to improve it by little modification, I decided to build a new function. It will appear in a short time under the name sinide.m.

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30 Jan 2014 will wehner

will wehner (view profile)

t=0:.01:1;
y=2*sin(2*pi*10*t+3)+5;

[f,a,phi,ave] = sinfapm(y,100)

Returns
f=2.486
a=-0.1283
phi=1.5719
ave=5.0035

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11 Oct 2009 John

John (view profile)

When I implement this function for noisy sine vawes, the amplitudes seem to be very far from reality. Often, amplitudes have even minus signs(?). Any ideas why ?

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18 Apr 2009 Pablo

Pablo (view profile)

txs a lot =)).
i need it that mean

24 Jul 2008 david sweeney

How do I get this file to run????

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31 May 2008 Ramesh Pachar