Velocity unsteady

[MaikFZJ]

compute_individual_velocity calculates unsteady velocity depending on frame_step at the beginning and end of the trajectory. The interval does not increasing gradually and has the current frame in the centre.

[schroedtert]

After discussion:

• leave current version in
• add new velocity methods, switch with parameter
  • exclude parts where not the whole frame interval is valid
  • use an adaptive approach (increase frame interval till it reaches full width)

[schroedtert]

Differences with some newly implemented functions:

• current/single sided: use only one side, if on the other less than frame_step frames are available
• cutting/excluded: use only frames where both sides are complete
• adaptive: use a balanced window, with as many frames available
• mixed/maximum range: use as many frames as possible

Results (without cutting, as no difference in the middle):

[schroedtert]

Added the above discussed methods:

• exclude border
• adaptive border
• single sided border

More detailed description here: https://pedpy.readthedocs.io/en/stable/user_guide.html#individual-speed