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+% DetectOKN360.m
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+%
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+% This function detects optokinetic nystagmus for 360 degrees data. It uses a
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+% two step process. In the first step it detects points were the direction
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+% difference around a point is greater than 90 degrees. In the second step
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+% it compares the FOV speed of the intervals. If it is above a threshold then
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+% it is considered as OKN
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+%
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+% NOTE: OKN is calculated only in FOV representation. Also saccades have to be
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+% annotated in advance.
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+%
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+% input:
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+% arffFile - file with ARFF data
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+% saccAttName - name of the saccade attribute
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+% saccValue - integer value representing saccades
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+%
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+% output:
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+% result - a logical vector of the same size as the data in the ARFF with true value
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+% when OKN occurs
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+
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+function result = DetectOKN360(arffFile, saccAttName, saccValue)
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+ c_minIntAngle = 90; % minimum angle between saccade and subsequent interval
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+ c_maxIntSaccAngle = 70; % maximum angle between saccades
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+ c_minIntSpeed = 10; % degrees/sec
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+ c_saccAttVal = saccValue;
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+ c_OKNlabel = 1;
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+
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+ [data, metadata, attributes] = LoadArff(arffFile);
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+ timeInd = GetAttPositionArff(attributes, 'time');
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+
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+ [eyeFovVec, eyeHeadVec, headVec] = GetCartVectors(data, metadata, attributes);
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+
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+ saccInts = GetIntervalsIndexArff(data, attributes, saccAttName, c_saccAttVal);
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+
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+ result = zeros(size(data,1),1);
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+ attInd = GetAttPositionArff(attributes, saccAttName);
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+ %result(data(:,attInd) == c_saccAttVal) = c_OKNlabel;
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+ for ind=1:size(saccInts,1)-1
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+ saccDir1 = eyeFovVec(saccInts(ind,2),:) - eyeFovVec(saccInts(ind,1),:);
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+ saccDir2 = eyeFovVec(saccInts(ind+1,2),:) - eyeFovVec(saccInts(ind+1,1),:);
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+
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+ % inter-saccadic direction
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+ intSaccDir = eyeFovVec(saccInts(ind+1,1)-1,:) - eyeFovVec(saccInts(ind,2)+1,:);
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+
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+ if (sum(saccDir1) == 0 || sum(saccDir2) == 0 || sum(intSaccDir) == 0)
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+ continue;
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+ end
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+
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+ saccDir1 = saccDir1 / norm(saccDir1);
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+ saccDir2 = saccDir2 / norm(saccDir2);
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+ intSaccDir = intSaccDir / norm(intSaccDir);
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+
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+ relDirSacc = GetDispersion(saccDir1, saccDir2);
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+ relDirIntSacc1 = GetDispersion(saccDir1, intSaccDir);
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+ relDirIntSacc2 = GetDispersion(saccDir2, intSaccDir);
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+ dur = data(saccInts(ind+1,1)-1, timeInd) - data(saccInts(ind,2)+1, timeInd);
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+ dur = dur / 1000000;
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+ ampl = GetDispersion(eyeFovVec(saccInts(ind+1,1)-1,:), eyeFovVec(saccInts(ind,2)+1,:));
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+ speed = ampl / dur;
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+
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+ if (relDirSacc < c_maxIntSaccAngle && ...
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+ relDirIntSacc1 > c_minIntAngle && ...
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+ relDirIntSacc2 > c_minIntAngle && ...
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+ speed > c_minIntSpeed)
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+ %if ((relDirIntSacc1 > c_minIntAngle || ...
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+ % relDirIntSacc2 > c_minIntAngle) && ...
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+ % speed > c_minIntSpeed)
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+ result(saccInts(ind,2)+1:saccInts(ind+1,1)-1) = c_OKNlabel;
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+ end
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+ end
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+
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+ % Iterate again through saccade intervals and make sure that at least two
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+ % OKN intervals exist continuously.
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+ for ind=2:size(saccInts,1)-1
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+ if (result(saccInts(ind,2)+1) == c_OKNlabel)
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+ if (result(saccInts(ind,1) -1) ~= c_OKNlabel && ... % previous interval
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+ result(saccInts(ind+1,2)+1) ~= c_OKNlabel) % next interval
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+ result(saccInts(ind,2)+1:saccInts(ind+1,1)-1) = 0;
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+ end
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+ end
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+ % assign OKN label to saccades between OKN intervals
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+ if (result(saccInts(ind,1) -1) == c_OKNlabel && ...
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+ result(saccInts(ind,2)+1) == c_OKNlabel)
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+ result(saccInts(ind,1):saccInts(ind,2)) = c_OKNlabel;
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+ end
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+ end
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+
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+ confInd = GetAttPositionArff(attributes, 'confidence');
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+ result(data(:,confInd) < 1) = 0;
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+
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+ result = logical(result);
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+end
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