import java.util.*; /** * For Descriptive Statistics * @AUTHOR: Aayushman Choudhary * @YEAR: 2017 * REMEMBER : AFTER ALL DATA HAVE BEEN ADDED, * call update(). * else some calculations will be wrong. */ public class Data { private ArrayList list; public Data() { this.list = new ArrayList(); } public int count() { int i = 0; for (Datum d : list) { i += d.f; } return i; } public void add(int f, double x) { list.add(new Datum(f, x)); sort(); } public void remove(int f, double x) { Iterator iter = list.iterator(); while (iter.hasNext()) { Datum d = iter.next(); if (d.f == f && d.x == x) { iter.remove(); } } sort(); } public double sum() { double sum = 0; for (Datum d : list) { sum += d.y; } return sum; } public double average() { return sum() / count(); } public double mode() { sort(); float ii = 0f; for (Datum d : list) { if (d.f > ii) { ii = d.f; } } double pl = 0; int ct = 0; for (Datum d : list) { if (d.f == ii) { pl += d.x; ct++; } } pl /= ct; return pl; } public double median() { sort(); float ii = 0f; for (Datum d : list) { ii += d.f; if (ii > (float)(count() / 2)) { return d.x; } } return 0; } public ArrayList list() { return list; } /** */ public ArrayList pondList() { ArrayList pl = new ArrayList(); for (Datum d : list) { pl.add(d.y); } return pl; } public ArrayList deviationList() { ArrayList pl = new ArrayList(); for (Datum d : list) { pl.add(d.X); } return pl; } public ArrayList deviationListSqr() { ArrayList pl = new ArrayList(); for (Datum d : list) { pl.add(d.XX); } return pl; } /** variance */ public double var() { double sum = 0; for (Datum d : list) { sum += d.XX; } return sum / count(); } /** standard deviation */ public double stDev() { return Math.sqrt(var()); } private void sort() { Collections.sort(list); } @Override public String toString() { return list.toString(); } /** after all data have been added, update */ public void update() { for (Datum d : list) { d.X = d.x - average(); d.XX = d.X * d.X; } } //Inner class Datum that hold and wrap data class Datum implements Comparable { public int f; // frequency public double x; // value public double y; // ponderation (f*x); public double X; // deviation from the mean public double XX; // deviation squared public Datum(int f, double x) { this.f = f; this.x = x; y = x * f; } // compareTo() and equals() methods are necessary for sorting // the 2 methods use the same comparison process for integrity @Override public int compareTo(Object p1) { return Double.compare(x, ((Datum)p1).x); } @Override public boolean equals(Object o) { return Double.compare(x, ((Datum)o).x) == 1; } @Override public String toString() { return "| " + f + " | " + x + " | " + y + " | " + X + " | " + XX + " |\n"; } } // end of Inner class Datum } //End of class Data

Descriptive Statistics (class)