FAQ: How can I filter and / or merge fixations?
In Data Viewer fixations can be merged with with nearby neighbors based on amplitude and duration criteria by enabling the Merge Nearby Fixations property of the preferences (Preferences tab in Inspector window -> Data Filters -> Merge Nearby Fixations). This will apply the specified amplitude and duration parameters to merge fixations fulfilling the criteria.


Alternatively, Data Viewer's 4-Stage Fixation Cleaning tool can be used to apply a multi-stage approach to clean up / merge fixations based on multiple criteria. This option is intended for use only by reading researchers who want to follow a cleaning procedure that is established in their field. To perform this action, right click in the top panel of the Data tab in the Inspector window and select "Perform 4-stage Fixation Cleaning".


A prompt with options to perform the four stages will appear and the stages can be applied individually or in sequence:
  1. STAGE 1 - For each Interest Area, Data Viewer checks for each fixation whether it’s time duration is shorter or equal to the STAGE 1 duration threshold. If not, the current fixation will not be cleaned; if it is, Data Viewer checks the duration and distance of the fixation immediately before and after the current fixation. The fixation will be merged to the neighboring fixation if its duration is longer than the threshold value and its distance along the X axis (in degrees) from the current fixation is shorter or equal to the STAGE 1 distance threshold. If both the previous and next fixations meet the above criterion, the current fixation will be merged to the longer one of the two.
  2. STAGE 2 - This stage is similar to STAGE 1 except you should set shorter fixation duration and a longer distance value relative to STAGE 1 so that additional fixation merging can occur.
  3. STAGE 3 - Data Viewer rechecks all of the data to find Interest Areas that include at least three fixations smaller than the STAGE 3 threshold duration and no fixations larger than the threshold duration. It then merges the shorter fixations into the larger ones.
  4. STAGE 4 - Data Viewer rechecks all fixations and deletes every fixation that is shorter than minimum duration or larger than the maximum duration threshold.