Class for finding the median of a two-dimensional space

Question

I have a simple static class that it's purpose is given an RDD of Point to find the median of each dimension and return that as a new Point using Spark's reduce functions.

This is the class:

public class MedianPointFinder { public static Point findMedianPoint(JavaRDD<Point> points) { Point biggestPointByXDimension = points.reduce((a, b) -> getBiggestPointByXDimension(a, b)); Point biggestPointByYDimension = points.reduce((a, b) -> getBiggestPointByYDimension(a, b)); double xDimensionMedian = biggestPointByXDimension.getX() / 2.0; double yDimensionMedian = biggestPointByYDimension.getY() / 2.0; return new Point(xDimensionMedian, yDimensionMedian); } private static Point getBiggestPointByXDimension(Point first, Point second) { return first.getX() > second.getX() ? first : second; } private static Point getBiggestPointByYDimension(Point first, Point second) { return first.getY() > second.getY() ? first : second; } }

Point class is a simple class for storing an (x, y) point.

My understanding of median is the middle element out of N elements if the N elements were sorted. You are finding the highest element and dividing its value by 2. Is that what you really meant to do? For example, given three x coordinates 1 2 9 I consider the median to be 2 not 4.5. — JS1
– JS1, Commented Nov 28, 2014 at 6:08

Gerold Broser · Accepted Answer · 2014-11-27 22:43:11Z

I guess your Point is not a java.awt.Point since that holds x and y as int and you're using double.

Why not getting rid of your Point class by making the "Finder" class itself a MedianPoint?

import java.awt.geom.Point2D; public class MedianPoint extends Point2D.Double { public MedianPoint(JavaRDD<Point> points) { super( /* your x calculation */, /* your y calculation */ ); } private static Point2D.Double greaterByXOf(Point2D.Double p1, Point2D.Double p2) { // ... } private static Point2D.Double greaterByYOf(Point2D.Double p1, Point2D.Double p2) { // ... } } // MedianPoint

I do need my Point class for some methods that I have created in it that does not exist in Point2D but I guess what I could do is wrap Point2D with my Point class and then do MedianPoint extends Point. — Aki K
– Aki K, Commented Nov 26, 2014 at 9:15
Are there other reasons why you have to stick to Point? Which make moving Point's methods into MedianPoint impossible? — Gerold Broser
– Gerold Broser, Commented Nov 26, 2014 at 10:47
No, not really. I just have it for providing a limited API and adding some functionality. I have posted my revised Point class here codereview.stackexchange.com/questions/70902/… — Aki K
– Aki K, Commented Nov 26, 2014 at 11:21

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