| 1 | /** |
| 2 | * |
| 3 | */ |
| 4 | package de.uka.ipd.sdq.probfunction.math.apache.distribution; |
| 5 | |
| 6 | import org.apache.commons.math.MathException; |
| 7 | import org.apache.commons.math.distribution.AbstractIntegerDistribution; |
| 8 | |
| 9 | /** |
| 10 | * @author joerg |
| 11 | * |
| 12 | */ |
| 13 | public class UniformIntDistributionImpl extends AbstractIntegerDistribution { |
| 14 | |
| 15 | |
| 16 | /** |
| 17 | * |
| 18 | */ |
| 19 | private static final long serialVersionUID = 4771624459254238355L; |
| 20 | int a,b; |
| 21 | int intCount; |
| 22 | |
| 23 | |
| 24 | public int getA() { |
| 25 | return a; |
| 26 | } |
| 27 | |
| 28 | |
| 29 | public int getB() { |
| 30 | return b; |
| 31 | } |
| 32 | |
| 33 | |
| 34 | |
| 35 | public UniformIntDistributionImpl(int a, int b) throws MathException |
| 36 | { |
| 37 | if(b<a) |
| 38 | throw new MathException("Second value has to be greater than first value of interval"); |
| 39 | |
| 40 | this.a = a; |
| 41 | this.b = b; |
| 42 | intCount = b - a + 1; |
| 43 | |
| 44 | |
| 45 | } |
| 46 | |
| 47 | |
| 48 | /* (non-Javadoc) |
| 49 | * @see org.apache.commons.math.distribution.AbstractIntegerDistribution#cumulativeProbability(int) |
| 50 | */ |
| 51 | @Override |
| 52 | public double cumulativeProbability(int x) throws MathException { |
| 53 | if(x<a) |
| 54 | return 0; |
| 55 | else if(x>b) |
| 56 | return 1; |
| 57 | |
| 58 | return (x-a+1)/intCount; |
| 59 | } |
| 60 | |
| 61 | /* (non-Javadoc) |
| 62 | * @see org.apache.commons.math.distribution.AbstractIntegerDistribution#getDomainLowerBound(double) |
| 63 | */ |
| 64 | @Override |
| 65 | protected int getDomainLowerBound(double p) { |
| 66 | return a; |
| 67 | } |
| 68 | |
| 69 | /* (non-Javadoc) |
| 70 | * @see org.apache.commons.math.distribution.AbstractIntegerDistribution#getDomainUpperBound(double) |
| 71 | */ |
| 72 | @Override |
| 73 | protected int getDomainUpperBound(double p) { |
| 74 | return b; |
| 75 | } |
| 76 | |
| 77 | /* (non-Javadoc) |
| 78 | * @see org.apache.commons.math.distribution.IntegerDistribution#probability(int) |
| 79 | */ |
| 80 | @Override |
| 81 | public double probability(int x) { |
| 82 | if(x<a||x>b) |
| 83 | return 0; |
| 84 | |
| 85 | return 1/intCount; |
| 86 | } |
| 87 | |
| 88 | public double getMean() |
| 89 | { |
| 90 | return (a+b)/2; |
| 91 | } |
| 92 | |
| 93 | public double getVariance() |
| 94 | { |
| 95 | return (-1.0*intCount*intCount)/12.0; |
| 96 | } |
| 97 | |
| 98 | } |