pymovements.gaze.Experiment.pos2vel

Experiment.pos2vel(arr: list[float] | list[list[float]] | np.ndarray, method: str = 'smooth', **kwargs: int | float | str) → np.ndarray

Compute velocity time series from 2-dimensional position time series.

Methods ‘smooth’, ‘neighbors’ and ‘preceding’ are adapted from

Engbert et al.: Microsaccade Toolbox 0.9.

Parameters:

• arr (list[float] | list[list[float]] | np.ndarray) – Continuous 2D position time series.

• method (str) – Computation method. See pos2vel() for details. (default: ‘smooth’)

• **kwargs (int | float | str) – Additional keyword arguments used for savitzky golay method.

Returns:

Velocity time series in input_unit / sec

Return type:

np.ndarray

Raises:

ValueError – If selected method is invalid, input array is too short for the selected method or the sampling rate is below zero

Examples

>>> experiment = Experiment(
...     screen_width_px=1280,
...     screen_height_px=1024,
...     screen_width_cm=38,
...     screen_height_cm=30,
...     distance_cm=68,
...     origin='upper left',
...     sampling_rate=1000.0,
... )
>>> arr = [[0., 0.], [1., 1.], [2., 2.], [3., 3.], [4., 4.], [5., 5.]]
>>> experiment.pos2vel(
...    arr=arr,
...    method="smooth",
... )
array([[ 500.,  500.],
       [1000., 1000.],
       [1000., 1000.],
       [1000., 1000.],
       [1000., 1000.],
       [ 500.,  500.]])