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
tic 
% 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(length(vel), 1)];
eyeData(vel < velocityThreshold, 4) = 1;

% collapse consecutive points into "event regions" (fixation/saccade)
startFixIdx = find(diff(eyeData(:,4))==1)+1;
endFixIdx = find(diff(eyeData(:,4))==-1);
if(endFixIdx(1)<startFixIdx(1))
    endFixIdx = endFixIdx(2:end);
end

if size(endFixIdx,1)<size(startFixIdx,1)
    endFixIdx(end+1) = size(eyeData,1);
end

% compute centroids
for i=1:size(endFixIdx,1)
    meanX = mean(eyeData(startFixIdx(i):endFixIdx(i),2));
    meanY = mean(eyeData(startFixIdx(i):endFixIdx(i),3));
    startTime = eyeData(startFixIdx(i),1);
    duration = eyeData(endFixIdx(i),1)-eyeData(startFixIdx(i),1);
    fixations = [fixations; [meanX meanY startTime duration]];
end
toc
% return found fixations

end