# Algorithm-Implementations Show Average_test.java Source code

1. package average;
2.
3. import org.junit.Test;
4. import java.util.stream.DoubleStream;
5. import static org.junit.Assert.*;
6.
7. /**
8.  * @author Joshua Moody (joshimoo@hotmail.de)
9.  */
10. public class AverageTest {
11.     private static final double DELTA = 0.01;
12.
13.     @Test
14.     public void testAverageInequality() throws Exception {
15.         double[] numbers = new double[] { 1, 2, 3, 4, 5 };
16.
17.         /**
18.          * Mean Inequalities:
19.          * Some means are in a constant relationship to one another.
20.          * If we denote the arithmentic mean of x and y by A,
21.          * their geometric mean by G,
22.          * their harmonic mean by H,
23.          * their root mean square (quadratic mean) by R,
24.          * and their contraharmonic mean by C,
25.          *
26.          * then the following chain of inequalities is always true
27.          * C >= R >= A >= G >= H
28.          */
29.
30.         double contraHarmonic = Average.contraHarmonicMean(numbers);
32.         double arithmetic = Average.arithmeticMean(numbers);
33.         double geometric = Average.geometricMean(numbers);
34.         double harmonic = Average.harmonicMean(numbers);
35.         assertTrue("Your Average inequalities are not correct", (contraHarmonic >= quadratic) && (quadratic >= arithmetic) && (arithmetic >= geometric) && (geometric >= harmonic));
36.     }
37.
38.     @Test
39.     public void testArithmeticMean() throws Exception {
40.         double[] numbers = new double[] { 1, 2, 3, 4, 5 };
41.         double expected = DoubleStream.of(numbers).average().getAsDouble();
42.         assertEquals(expected, Average.arithmeticMean(numbers), DELTA);
43.     }
44.
45.     @Test
46.     public void testWeightedMean() throws Exception {
47.         double[] numbers = new double[] { 1, 2, 3, 4, 5 };
48.         double[] weights = new double[] { 1, 1, 1, 1, 1 };
49.         double expected = DoubleStream.of(numbers).average().getAsDouble();
50.         assertEquals(expected, Average.weightedMean(numbers, weights), DELTA);
51.     }
52.
53.     @Test
54.     public void testHarmonicMean() throws Exception {
55.         // n/(1/x1 + 1/x2 + ... + 1/xn)
56.         double[] numbers = new double[] { 1, 2, 3, 4, 5 };
57.         double expected = numbers.length / DoubleStream.of(numbers).map(x -> 1.0 / x).sum();
58.         assertEquals(expected, Average.harmonicMean(numbers), DELTA);
59.     }
60.
61.     @Test
62.     public void testContraHarmonicMean() throws Exception {
63.         double[] numbers = new double[] { 1, 2, 3, 4, 5 };
64.         double expected = DoubleStream.of(numbers).map(x -> Math.pow(x, 2.0)).sum() / DoubleStream.of(numbers).sum();
65.         assertEquals(expected, Average.contraHarmonicMean(numbers), DELTA);
66.     }
67.
68.     @Test
69.     public void testGeometricMean() throws Exception {
70.         // (x1*x2*...xn) ^ (1/n)
71.         double[] numbers = new double[] { 1, 2, 3, 4, 5 };
72.         double expected = Math.pow((numbers * numbers * numbers * numbers * numbers), 1.0 / numbers.length);
73.         assertEquals(expected, Average.geometricMean(numbers), DELTA);
74.     }
75.
76.     @Test
77.     public void testQuadraticMean() throws Exception {
78.         // sqrt((x1)^2+(x2)^2+(x3)^2+...+(xn)^2 /n)
79.         double[] numbers = new double[] { 1, 2, 3, 4, 5 };
80.         double expected = Math.sqrt(DoubleStream.of(numbers).map(x -> Math.pow(x, 2)).sum() / numbers.length);
82.     }
83.
84.     @Test
85.     public void testGeneralizedMean() throws Exception {
86.         // y-root((x1)^y+(x2)^y+(x3)^y+...+(xn)^y / n)
87.         double[] numbers = new double[] { 1, 2, 3, 4, 5 };
88.         double power = 4;
89.         double expected = Math.pow((DoubleStream.of(numbers).map(x -> Math.pow(x, 4)).sum() / numbers.length), 1.0 / power);
90.         assertEquals(expected, Average.generalizedMean(numbers, power), DELTA);
91.     }
92.
93.     @Test
94.     public void testMidrange() throws Exception {
95.         double[] numbers = new double[] { 1, 2, 3, 4, 5 };
96.         double expected = (numbers + numbers[numbers.length - 1]) / 2.0;
97.         assertEquals(expected, Average.midrange(numbers), DELTA);
98.     }
99.
100.     @Test
101.     public void testMedianEven() throws Exception {
102.         double[] numbers = new double[] { 1, 2, 3, 4, 5, 6};
103.         double expected = (numbers[(numbers.length / 2) - 1] + numbers[numbers.length / 2]) / 2.0;
104.         assertEquals(expected, Average.median(numbers), DELTA);
105.     }
106.
107.     @Test
108.     public void testMedianOdd() throws Exception {
109.         double[] numbers = new double[] { 1, 2, 3, 4, 5 };
110.         double expected = numbers[((int) Math.floor(numbers.length / 2))];
111.         assertEquals(expected, Average.median(numbers), DELTA);
112.     }
113.
114.     @Test
115.     public void testMode() throws Exception {
116.         // frequency based average
117.         double[] numbers = new double[] { 1, 2, 3, 3, 3, 4, 5 };
118.         double expected = 3;
119.         assertEquals(expected, Average.mode(numbers), DELTA);
120.     }
121. }
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