zipfdistributiontest.java

一个自然语言处理的Java开源工具包。LingPipe目前已有很丰富的功能

package com.aliasi.test.unit.stats;

import com.aliasi.stats.ZipfDistribution;

import com.aliasi.test.unit.BaseTestCase;


public class ZipfDistributionTest extends BaseTestCase {

    public void testZero() {
    assertTrue(true);
    }

    public void testExs() {
    try {
        new ZipfDistribution(-1);
        fail();
    } catch (IllegalArgumentException e) {
        assertTrue(true);
    }
    }

    public void testDistro() {

    ZipfDistribution dist = new ZipfDistribution(3);
    assertEquals(3,dist.numOutcomes());
    double sum = 1.0 + 1.0/2.0 + 1.0/3.0;

    double p1 = 1.0/sum;
    double p2 = 1.0/2.0/sum;
    double p3 = 1.0/3.0/sum;

    assertEquals(p1,dist.probability(1),0.0005);
    assertEquals(p2,dist.probability(2),0.0005);
    assertEquals(p3,dist.probability(3),0.0005);
    assertEquals(0.0,dist.probability(0),0.0005);
    assertEquals(0.0,dist.probability(-1),0.0005);
    assertEquals(0.0,dist.probability(20),0.0005);
    
    double[] probs = ZipfDistribution.zipfDistribution(3);
    assertEquals(p1,probs[0],0.0005);
    assertEquals(p2,probs[1],0.0005);
    assertEquals(p3,probs[2],0.0005);

    assertEquals(-( p1*com.aliasi.util.Math.log2(p1)
            + p2*com.aliasi.util.Math.log2(p2)
            + p3*com.aliasi.util.Math.log2(p3) ),
             dist.entropy(),
             0.0005);

    }

    public void testDistro2() {
    ZipfDistribution distro = new ZipfDistribution(100);
    double sum = 0.0;
    for (int i = 0; i < 100; ++i)
        sum += distro.probability(i);
    assertEquals(1.0,sum,0.005);
    
    assertEquals(2.0,distro.probability(1)/distro.probability(2),0.001);
    }

}