Sine fitting

Determine parameters of a noisy sine function


Updated 8 Dec 2020

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sineFit is a function to detect the parameters of a noisy sine curve, even less than one period long.
It requires only x and y values and no additional parameters as input.
It is tested with R2016a and R2020a.
The mean calculation time is on my PC 13 ms with a maximum of 2400 ms.

optional: plot graphics if ommited. Do not plot if 0
x and y values, y = offs + amp * sin(2pi * f * x + phi) + noise
SineParams(1):offset (offs)
SineParams(2): amplitude (amp)
SineParams(3): frequency (f)
SineParams(4): phaseshift (phi)
SineParams(5): MSE , if negative then SineParams are from FFT

This is a brief and not exact description of the program flow.
• Estimate the offset by the mean of all y values.
• Build the FFT with heavy zero padding.
• Take the frequency, amplitude and phase of the largest FFT peak.
If the frequency is at the Nyquist limit or the period is less than one, add extra frequencies for evaluation.
• Take those values as initial values for the regressions.
• Take the resulting MSE as rating.
• Exclude results above Nyquist frequency.
• Depending on the number of samples and the MSE, set a limit for an accepted amplitude in relation to the FFT amplitude.
• If the amplitude from regression is higher than the accepted amplitude, take the FFT parameters.

A demonstration GUI is included.
For more information read the "ReadMe.pdf".

Cite As

Peter Seibold (2023). Sine fitting (, MATLAB Central File Exchange. Retrieved .

MATLAB Release Compatibility
Created with R2016a
Compatible with R2020a and later releases
Platform Compatibility
Windows macOS Linux

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Version Published Release Notes

Some changes in sineFitDemo in respect to 'run xy.mat'


Minor changes


No toolbox required anymore


Simplified code, faster processing, improved to work down to 0.1 periods, some more correct detections.

Image changed


Totally new approach with Fourier transformation results as initial parameters for fitting function.

Description corrected