frame_lag

mdtools.check.frame_lag(lag, every, n_frames_tot=None, allow_zero=False, verbose=True)[source]

Check if a frame lag (‘lag time’) is chosen properly.

Check if a frame lag (‘lag time’) is chosen properly with respect to the total number of frames in the trajectory and the interval between frames that are/were actually read.

The frame lag must meet the following requirements:

Must be greater than zero (if allow_zero is True, zero is also possible)

Must not be greater than n_frames_tot (if supplied).

Must be an integer multiple of every.

Parameters:

lag (int) – The frame lag, e.g. the number of frames between restarting points.
every (int) – Intervall used while reading the trajectory, i.e. only every n-th frame of the trajectory is/was actually read.
n_frames_tot (int, optional) – The total number of frames in the trajectory.
allow_zero (bool, optional) – If True, lag can also be zero.
verbose (bool, optional) – If True (default), any changes to lag are printed to standard output.

Returns:

lag (int) – The input or a corrected value.
effective_lag (int) – An effective frame lag. If e.g. only every tenth frame of the trajectory is read and you want a frame lag of fifty, the effective frame lag is five.