Reading SimpleGazeTracker data file for offline analysis

SimpleGazeTracker CSV file can be imported to Matlab/Octave workspace by using ‘ReadDataFile’ command. Import will take several minutes if the data file contains hundreds of trials.

data = SimpleGazeTracker('ReadDataFile','data.csv')

data =

  1x240 struct array containing the fields:

    STARTREC
    T
    L
    R
    LP
    RP
    MSG
    C
    CAL
    PARAM

Member	Data type	Description
STARTREC	1x6 numerical array	Date of starting recording (Year, Month, Day, Hour, Minute, Second).
T	Nx1 numerical array	Timestamps (N = number of samples).
L	Nx2 numerical array	Gaze position of the left eye (N = number of samples). The 1st and 2nd columns represent horizontal and vertical position, respectively.
R	Nx2 numerical array	Gaze position of the right eye (N = number of samples). The 1st and 2nd columns represent horizontal and vertical position, respectively.
LP	Nx1 numerical array	Area of left pupil (unit is pixel^2).
RP	Nx1 numerical array	Area of right pupil (unit is pixel^2).
MSG	Nx2 Cell array	The 1st column holds timestamp. The 2nd column holds messages.
C	(reserved)	(reserved)
CAL	MxN numerical array	Precision and accuracy at each calibration point (M = number of calibration points, N = 6 or 10). Data layout is the same as that in SimpleGazeTracker data file. New feature in 0.3.0.
PARAM	Scalar structure	Parameters embedded in the data file.

Following code returns recording date of the 4th trial.

octave-3.6.4.exe:34> data(4).STARTREC
ans =

   2013      2     27     13     10     14

Following code plots the horizontal gaze position of the left eye during the 1st trial.

octave-3.6.4.exe:38> plot(data(1).T, data(1).L(:,1))

Following code shows X-Y plot of the gaze position of the left eye during the 1st trial.

octave-3.6.4.exe:40> plot(data(1).L(:,1), data(1).L(:,2), 'r.-')

MSG member holds messages inserted during the trial.

octave-3.6.4.exe:45> data(45).MSG
ans =
{
  [1,1] = 0
  [2,1] =  598.80
  [3,1] =  2013.4
  [4,1] =  2163.4
  [1,2] = TRIAL45 300 1 -150
  [2,2] = START
  [3,2] = FIXOFF
  [4,2] = TRGON
}

octave-3.6.4.exe:46> data(45).MSG{3,1} %timestamp of the 3rd message
ans =  2013.4

octave-3.6.4.exe:47> data(45).MSG{3,2} %message of the 3rd message
ans = FIXOFF

PARAM member holds parameters embedded in the data file. Usually, embedded parameters are constant during recording. Althogh these parameters are embedded to be used by GazeParser library, they may be useful for data analysis on Matlab/Octave.

octave-3.6.4.exe:50> data(1).PARAM

ans =

  scalar structure containing the fields:

    SimpleGazeTrackerDataFile = [](0x0)
    TRACKER_VERSION = 0.5.1
    DATAFORMAT =
    {
      [1,1] = T
      [1,2] = X
      [1,3] = Y
      [1,4] = P
    }
    SACCADE_MINIMUM_DURATION = 12
    SACCADE_ACCELERATION_THRESHOLD = 3800.0
    SCREEN_WIDTH = 1920
    FILTER_WN = 0.25
    DOTS_PER_CENTIMETER_H = 37.7
    TRACKER_ORIGIN = BottomLeft
    RECORDED_EYE = L
    FILTER_ORDER = 3
    BLINK_MINIMUM_DURATION = 50
    FILTER_SIZE = 5
    FILTER_TYPE = butter_filtfilt
    DOTS_PER_CENTIMETER_V = 37.7
    VIEWING_DISTANCE = 57.2957795131
    SACCADE_VELOCITY_THRESHOLD = 40.0
    SCREEN_ORIGIN = BottomLeft
    FIXATION_MINIMUM_DURATION = 12
    SCREEN_HEIGHT = 1080