Functions for Statistics
/* * Copyright WizTools.org * Licensed under the Apache License, Version 2.0: * http://www.apache.org/licenses/LICENSE-2.0 *///package org.wiztools.commons; import java.util.ArrayList; import java.util.Arrays; import java.util.HashMap; import java.util.Iterator; import java.util.List; import java.util.Map; /** * * @author subWiz */publicfinalclass Statistics { private Statistics() {} privatestaticfinal String LOG_ARRAY_LENGTH_0 = "Length of array cannot be 0!"; /* MEAN */publicstaticint mean(finalint[] list) throws IllegalArgumentException { if(list.length == 0) { thrownew IllegalArgumentException(LOG_ARRAY_LENGTH_0); } int sum = 0; for(int n: list) { sum += n; } return sum / list.length; } publicstaticlong mean(finallong[] list) throws IllegalArgumentException { if(list.length == 0) { thrownew IllegalArgumentException(LOG_ARRAY_LENGTH_0); } long sum = 0; for(long n: list) { sum += n; } return sum / list.length; } publicstaticfloat mean(finalfloat[] list) throws IllegalArgumentException { if(list.length == 0) { thrownew IllegalArgumentException(LOG_ARRAY_LENGTH_0); } float sum = 0; for(float n: list) { sum += n; } return sum / list.length; } publicstaticdouble mean(finaldouble[] list) throws IllegalArgumentException { if(list.length == 0) { thrownew IllegalArgumentException(LOG_ARRAY_LENGTH_0); } float sum = 0; for(double n: list) { sum += n; } return sum / list.length; } /* MEDIAN */publicstaticint median(finalint[] list) throws IllegalArgumentException { if(list.length < 1) { thrownew IllegalArgumentException(); } Arrays.sort(list); if((list.length % 2) == 0) { // is even finalint idx = list.length / 2; return (list[idx] + list[idx-1]) / 2; } else { // is odd finalint idx = list.length / 2; return list[idx]; } } /* MODE */privatestaticclass ModeCompute <T extends Number> { private Map<T, Integer> map = new HashMap<T, Integer>(); privateint maxFrequency = 0; void add(T t) { finalint count = (map.get(t) == null)? 1: (map.get(t) + 1); // Update map: map.put(t, count); // Update maxFrequency: if(count > maxFrequency) maxFrequency = count; } List<T> getMode() { List<T> out = new ArrayList<T>(); for(Map.Entry<T, Integer> entry: map.entrySet()) { if(entry.getValue() == maxFrequency) { out.add(entry.getKey()); } } return out; } } publicstaticint[] mode(finalint[] list) throws IllegalArgumentException { if(list.length == 0) { thrownew IllegalArgumentException(LOG_ARRAY_LENGTH_0); } final ModeCompute<Integer> modeComp = new ModeCompute<Integer>(); for(int i=0; i<list.length; i++) { modeComp.add(list[i]); } final List<Integer> l = modeComp.getMode(); // Prepare the output array: finalint[] out = newint[l.size()]; Iterator<Integer> itr = l.iterator(); for(int i=0; i<out.length; i++) { out[i] = itr.next(); } return out; } } Related examples in the same category
