function [ fixations ] = labelFixationsViaIVT( EyeMove, mode, velocityThreshold )
%%% labels data by applying an IVT fixation algorithms
%%% on the given EyeMove data
%%% 
%%% EyeMove: eye movements of the participant [time|Lx|Ly|Rx|Ry|Hx|Hy]
%%% mode: L, R
%%% velocityThreshold: point-to-point velocity threshold between fixation
%%% and saccade (pixel based)
%%%
%%% Output:
%%% fixation Nx4 [posX | posY | startTimestamp | duration]
%%% Created by: Jakob Karolus
%%% Last updated: 2016-06-29


switch upper(mode)
    case 'L'
        eyeData = EyeMove(:,1:3);
    case 'R'
        eyeData = [EyeMove(:,1) EyeMove(:, 4:5)];
end

% Implement your version of IVT here

% calculate the velocities
velX = diff(eyeData(:,2));
velY = diff(eyeData(:,3));
vel = sqrt(velX.^2+velY.^2);
vel = [vel; 0];

% label fixation and saccade points
eyeData = [eyeData zeros(size(eyeData,1),1)];
eyeData(:,4) = vel<velocityThreshold;

% initializations of variables
fixations = [];
startedFixation = false;
fixationStartIndex = 0;

% collapse consecutive points into "event regions" (fixation/saccade)
for i=1:size(eyeData,1)
    % does a new fixation start (or we not analysing a fixation)
    if eyeData(i, 4) == 1 && startedFixation == false %(~startedFixation)
        startedFixation = true;
        fixationStartIndex = i;
    % if we are evaluating a fixation -> continue
    elseif eyeData(i,4) == 1 && startedFixation == true %(startedFixation)
        continue;
    % if we are not evaluating a fixation, and a new one doesn't start -> continue    
    elseif eyeData(i,4) == 0 && startedFixation == false %(~startedFixation)
        continue;
    % if a fixation ends
    else
        startedFixation = false;
        
        % create X centroid
        meanX = mean(eyeData(fixationStartIndex:i-1,2));
        
        % create Y centroid
        meanY = mean(eyeData(fixationStartIndex:i-1,3));
        
        % starttime
        startTime = eyeData(fixationStartIndex,1);
        
        % duration
        duration = eyeData(i,1)-startTime;
        
        fixations = [fixations; [meanX meanY startTime duration]];
    end    
    
end

% delete fixations that are shorter than 50ms
fixations = fixations(fixations(:,4)>=50,:);

end