Note
This is the documentation for the current state of the development branch of Qiskit Experiments. The documentation or APIs here can change prior to being released.
frequency¶
- frequency(x, y, filter_window=5, filter_dim=2)[source]¶
Get frequency of oscillating signal.
First this tries FFT. If the true value is likely below or near the frequency resolution, the function tries low frequency fit with
\[f_{\rm est} = \frac{1}{2\pi {\rm max}\left| y \right|} {\rm max} \left| \frac{dy}{dx} \right|\]given \(y = A \cos (2\pi f x + phi)\). In this mode, y data points are smoothed by a Savitzky-Golay filter to protect against outlier points.
Note
This function returns always positive frequency. This function is sensitive to the DC offset. This function assumes sorted, no-overlapping x values.
- Parameters:
x (ndarray) – Array of x values.
y (ndarray) – Array of y values.
filter_window (int) – Window size of Savitzky-Golay filter. This should be odd number.
filter_dim (int) – Dimension of Savitzky-Golay filter.
- Returns:
Frequency estimation of oscillation signal.
- Return type:
float