feat: change fixation / saccade output file format

[theDebbister]

Change fixations / saccade file format

Currently, fixations and saccades are parsed and written to separate files for each trial. This behaviour should be changed as it is more common to have them in one file as a sequence (for each trial).

Possible file formats

There are two file formats which are commonly used:

1. List both fixations and saccades as events per row, alternating fixations and saccades and consequently representing the actual event sequence. (my preference)
2. Encode saccades as features of fixations (done by data viewer). This means that each fixation gets a feature previous saccade and next saccade. For the two saccades, the saccade features are added, e.g., prev_saccade_duration, next_saccade_duration.
3. Other??

Pros and Cons of 1.

• File can very easily be filtered by event. If no saccades are needed, they can be filtered out
• More redundant columns. All events get all features not matter if a feature is only available for one event type
• It is possible to provide a script to convert it to the second format below. Probably easier to do this than vice versa...

Pros and Cons of 2.

• It is very common to study only fixations in reading and information on the, e.g., incoming saccade length in chars for a fixation is very commonly used.
• Hard to disentangle fixations and saccades again

Other open questions

• Which columns should be saved in the files? E.g., velocity etc. could be recalculated when reading the files and don't absolutely have to be in there.
• File name: currently, the file receives an event type suffix [Session ID]_trial_1_Lit_MagicMountain_6_[saccade/fixation].csv. Possibly best to replace this by "events".