pymovements.gaze.transforms.pos2vel

pymovements.gaze.transforms.pos2vel(*, sampling_rate: float, method: str, n_components: int, degree: int | None = None, window_length: int | None = None, padding: str | float | int | None = 'nearest', position_column: str = 'position', velocity_column: str = 'velocity') → pl.Expr

Compute velocitiy data from positional data.

Parameters:

• sampling_rate (float) – Sampling rate of input time series.

• method (str) – The method to use for velocity calculation.

• n_components (int) – Number of components in input column.

• degree (int | None) – The degree of the polynomial to use. This has only an effect if using savitzky_golay as calculation method. (default: None)

• window_length (int | None) – The window size to use. This has only an effect if using savitzky_golay as calculation method. (default: None)

• padding (str | float | int | None) – The padding to use. This has only an effect if using savitzky_golay as calculation method. (default: ‘nearest’)

• position_column (str) – The input position column name. (default: ‘position’)

• velocity_column (str) – The output velocity column name. (default: ‘velocity’)

Returns:

The respective polars expression.

Return type:

pl.Expr

Notes

There are three methods available for velocity calculation:

• savitzky_golay: velocity is calculated by a polynomial of fixed degree and window length. See savitzky_golay() for further details.

• five_point: velocity is calculated from the difference of the mean values of the subsequent two samples and the preceding two samples

• neighbors: velocity is calculated from difference of the subsequent sample and the preceding sample

• preceding: velocity is calculated from the difference of the current sample to the preceding sample