UniformIntDist.java

/*
 * Class:        UniformIntDist
 * Description:  discrete uniform distribution
 * Environment:  Java
 * Software:     SSJ
 * Copyright (C) 2001  Pierre L'Ecuyer and Universite de Montreal
 * Organization: DIRO, Universite de Montreal
 * @author
 * @since
 *
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 */
package umontreal.ssj.probdist;

public class UniformIntDist extends DiscreteDistributionInt {
   protected int i;
   protected int j;

   public UniformIntDist(int i, int j) {
      setParams(i, j);
   }
 
   public double prob(int x) {
      return prob(i, j, x);
   }
 
   public double cdf(int x) {
      return cdf(i, j, x);
   }
 
   public double barF(int x) {
      return barF(i, j, x);
   }
 
   public int inverseFInt(double u) {
      return inverseF(i, j, u);
   }
 
   public double getMean() {
      return getMean(i, j);
   }
 
   public double getVariance() {
      return getVariance(i, j);
   }
 
   public double getStandardDeviation() {
      return getStandardDeviation(i, j);
   }

   public static double prob(int i, int j, int x) {
      if (j < i)
         throw new IllegalArgumentException("j < i");
      if (x < i || x > j)
         return 0.0;
 
      return (1.0 / (j - i + 1.0));
   }

   public static double cdf(int i, int j, int x) {
      if (j < i)
         throw new IllegalArgumentException("j < i");
      if (x < i)
         return 0.0;
      if (x >= j)
         return 1.0;
 
      return ((x - i + 1) / (j - i + 1.0));
   }

   public static double barF(int i, int j, int x) {
      if (j < i)
         throw new IllegalArgumentException("j < i");
      if (x <= i)
         return 1.0;
      if (x > j)
         return 0.0;
 
      return ((j - x + 1.0) / (j - i + 1.0));
   }

   public static int inverseF(int i, int j, double u) {
      if (j < i)
         throw new IllegalArgumentException("j < i");
 
      if (u > 1.0 || u < 0.0)
         throw new IllegalArgumentException("u not in [0, 1]");
 
      if (u <= 0.0)
         return i;
      if (u >= 1.0)
         return j;
 
      return i + (int) (u * (j - i + 1.0));
   }

   public static double[] getMLE(int[] x, int n) {
      if (n <= 0)
         throw new IllegalArgumentException("n <= 0");
 
      double parameters[] = new double[2];
      parameters[0] = (double) Integer.MAX_VALUE;
      parameters[1] = (double) Integer.MIN_VALUE;
      for (int i = 0; i < n; i++) {
         if ((double) x[i] < parameters[0])
            parameters[0] = (double) x[i];
         if ((double) x[i] > parameters[1])
            parameters[1] = (double) x[i];
      }
      return parameters;
   }

   public static UniformIntDist getInstanceFromMLE(int[] x, int n) {
 
      double parameters[] = getMLE(x, n);
 
      return new UniformIntDist((int) parameters[0], (int) parameters[1]);
   }

   public static double getMean(int i, int j) {
      if (j < i)
         throw new IllegalArgumentException("j < i");
 
      return ((i + j) / 2.0);
   }

   public static double getVariance(int i, int j) {
      if (j < i)
         throw new IllegalArgumentException("j < i");
 
      return (((j - i + 1.0) * (j - i + 1.0) - 1.0) / 12.0);
   }

   public static double getStandardDeviation(int i, int j) {
      return Math.sqrt(UniformIntDist.getVariance(i, j));
   }

   public int getI() {
      return i;
   }

   public int getJ() {
      return j;
   }

   public void setParams(int i, int j) {
      if (j < i)
         throw new IllegalArgumentException("j < i");
 
      supportA = this.i = i;
      supportB = this.j = j;
   }

   public double[] getParams() {
      double[] retour = { i, j };
      return retour;
   }

   public String toString() {
      return getClass().getSimpleName() + " : i = " + i + ", j = " + j;
   }
 
}