Fix precision bugs in ConvexHull and SaccadeVelocity

- Remove (long) casts in ConvexHull that truncated floating-point values
- Return NaN instead of 0.0 when all velocities exceed threshold
- Fix writeCSV.csv line endings (CRLF to LF) for OpenCSV 5.x compatibility

Author: oscararenas12

src/main/java/com/github/thed2lab/analysis/ConvexHull.java

@@ -180,9 +180,8 @@ public int compare(Point2D.Double a, Point2D.Double b) {
                     return 0;
                 }
 
-                // use longs to guard against int-underflow
-                double thetaA = Math.atan2((long)a.y - lowest.y, (long)a.x - lowest.x);
-                double thetaB = Math.atan2((long)b.y - lowest.y, (long)b.x - lowest.x);
+                double thetaA = Math.atan2(a.y - lowest.y, a.x - lowest.x);
+                double thetaB = Math.atan2(b.y - lowest.y, b.x - lowest.x);
 
                 if(thetaA < thetaB) {
                     return -1;
@@ -193,11 +192,10 @@ else if(thetaA > thetaB) {
                 else {
                     // collinear with the 'lowest' point, let the point closest to it come first
 
-                    // use longs to guard against int-over/underflow
-                    double distanceA = Math.sqrt((((long)lowest.x - a.x) * ((long)lowest.x - a.x)) +
-                                                (((long)lowest.y - a.y) * ((long)lowest.y - a.y)));
-                    double distanceB = Math.sqrt((((long)lowest.x - b.x) * ((long)lowest.x - b.x)) +
-                                                (((long)lowest.y - b.y) * ((long)lowest.y - b.y)));
+                    double distanceA = Math.sqrt(((lowest.x - a.x) * (lowest.x - a.x)) +
+                                                ((lowest.y - a.y) * (lowest.y - a.y)));
+                    double distanceB = Math.sqrt(((lowest.x - b.x) * (lowest.x - b.x)) +
+                                                ((lowest.y - b.y) * (lowest.y - b.y)));
 
                     if(distanceA < distanceB) {
                         return -1;
@@ -235,9 +233,8 @@ else if(thetaA > thetaB) {
      */
     protected static Turn getTurn(Point2D.Double a, Point2D.Double b, Point2D.Double c) {
 
-        // use longs to guard against int-over/underflow
-        long crossProduct = (long) ((((long)b.x - a.x) * ((long)c.y - a.y)) -
-                            (((long)b.y - a.y) * ((long)c.x - a.x)));
+        double crossProduct = ((b.x - a.x) * (c.y - a.y)) -
+                              ((b.y - a.y) * (c.x - a.x));
 
         if(crossProduct > 0) {
             return Turn.COUNTER_CLOCKWISE;

src/main/java/com/github/thed2lab/analysis/SaccadeVelocity.java

@@ -159,13 +159,14 @@ static double getPeakVelocity(List<Double[]> saccadePoints) {
 		if (saccadePoints.size() == 0 || saccadePoints.size() == 1) {
 			return Double.NaN;
 		}
-		
+
 		final double PIXELS_TO_CM = 0.0264583333; // Convert from pixels to cms
 		final double VELOCITY_THRESHOLD = 700; // Maximum possible saccadic velocity
         final double PARTICIPANT_DISTANCE = 65; // assume an average distance of 65cm from the participant to the screen
         final double RADIAN_TO_DEGREES = 180/Math.PI;
         double peakVelocity = 0;
-		
+        boolean foundValidVelocity = false;
+
 		for (int i = 1; i < saccadePoints.size(); i++) {
 			Double[] currPoint = saccadePoints.get(i);
 			Double[] prevPoint = saccadePoints.get(i - 1);
@@ -174,19 +175,22 @@ static double getPeakVelocity(List<Double[]> saccadePoints) {
 			double y1 = currPoint[1];
 			double x2 = prevPoint[0];
 			double y2 = prevPoint[1];
-			
+
 			double dx = Math.sqrt(Math.pow(Math.abs(x1 - x2), 2) + Math.pow(Math.abs(y1 - y2), 2)) * PIXELS_TO_CM;
 			double dt = Math.abs(currPoint[2] - prevPoint[2]);
 			double amplitude = RADIAN_TO_DEGREES * Math.atan(dx/PARTICIPANT_DISTANCE);
-			
+
 			double velocity = amplitude/dt;
-			
-			if (velocity > peakVelocity && velocity <= VELOCITY_THRESHOLD) {
-				peakVelocity = velocity;
+
+			if (velocity <= VELOCITY_THRESHOLD) {
+				if (velocity > peakVelocity) {
+					peakVelocity = velocity;
+				}
+				foundValidVelocity = true;
 			}
 		}
-		
-		return peakVelocity;
+
+		return foundValidVelocity ? peakVelocity : Double.NaN;
 	}
 
     /**

src/test/java/com/github/thed2lab/analysis/SaccadeVelocityTest.java

@@ -31,14 +31,14 @@ public void testGetPeakVelocity_onePoint_returnNaN() {
    }
 
    @Test
-   public void testGetPeakVelocity_aboveThreshold_return0() {
+   public void testGetPeakVelocity_aboveThreshold_returnNaN() {
       List<Double[]> saccadePoints = List.of(
          new Double[]{0., 0., 0.},
          new Double[]{0., 10., 0.0001}
       );
-      // 2332.21914 > 700 => return 0
-      boolean isZero = SaccadeVelocity.getPeakVelocity(saccadePoints) == 0;
-      assertTrue(isZero);
+      // 2332.21914 > 700 => return NaN (excluded from statistics)
+      boolean isNaN = Double.isNaN(SaccadeVelocity.getPeakVelocity(saccadePoints));
+      assertTrue(isNaN);
    }
 
    @Test