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Diffstat (limited to 'src/main/java/org/apache/commons/math3/distribution/IntegerDistribution.java')
| -rw-r--r-- | src/main/java/org/apache/commons/math3/distribution/IntegerDistribution.java | 145 |
1 files changed, 145 insertions, 0 deletions
diff --git a/src/main/java/org/apache/commons/math3/distribution/IntegerDistribution.java b/src/main/java/org/apache/commons/math3/distribution/IntegerDistribution.java new file mode 100644 index 0000000..c188a78 --- /dev/null +++ b/src/main/java/org/apache/commons/math3/distribution/IntegerDistribution.java @@ -0,0 +1,145 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You 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 org.apache.commons.math3.distribution; + +import org.apache.commons.math3.exception.NumberIsTooLargeException; +import org.apache.commons.math3.exception.OutOfRangeException; + +/** Interface for distributions on the integers. */ +public interface IntegerDistribution { + /** + * For a random variable {@code X} whose values are distributed according to this distribution, + * this method returns {@code P(X = x)}. In other words, this method represents the probability + * mass function (PMF) for the distribution. + * + * @param x the point at which the PMF is evaluated + * @return the value of the probability mass function at {@code x} + */ + double probability(int x); + + /** + * For a random variable {@code X} whose values are distributed according to this distribution, + * this method returns {@code P(X <= x)}. In other words, this method represents the + * (cumulative) distribution function (CDF) for this distribution. + * + * @param x the point at which the CDF is evaluated + * @return the probability that a random variable with this distribution takes a value less than + * or equal to {@code x} + */ + double cumulativeProbability(int x); + + /** + * For a random variable {@code X} whose values are distributed according to this distribution, + * this method returns {@code P(x0 < X <= x1)}. + * + * @param x0 the exclusive lower bound + * @param x1 the inclusive upper bound + * @return the probability that a random variable with this distribution will take a value + * between {@code x0} and {@code x1}, excluding the lower and including the upper endpoint + * @throws NumberIsTooLargeException if {@code x0 > x1} + */ + double cumulativeProbability(int x0, int x1) throws NumberIsTooLargeException; + + /** + * Computes the quantile function of this distribution. For a random variable {@code X} + * distributed according to this distribution, the returned value is + * + * <ul> + * <li><code>inf{x in Z | P(X<=x) >= p}</code> for {@code 0 < p <= 1}, + * <li><code>inf{x in Z | P(X<=x) > 0}</code> for {@code p = 0}. + * </ul> + * + * If the result exceeds the range of the data type {@code int}, then {@code Integer.MIN_VALUE} + * or {@code Integer.MAX_VALUE} is returned. + * + * @param p the cumulative probability + * @return the smallest {@code p}-quantile of this distribution (largest 0-quantile for {@code p + * = 0}) + * @throws OutOfRangeException if {@code p < 0} or {@code p > 1} + */ + int inverseCumulativeProbability(double p) throws OutOfRangeException; + + /** + * Use this method to get the numerical value of the mean of this distribution. + * + * @return the mean or {@code Double.NaN} if it is not defined + */ + double getNumericalMean(); + + /** + * Use this method to get the numerical value of the variance of this distribution. + * + * @return the variance (possibly {@code Double.POSITIVE_INFINITY} or {@code Double.NaN} if it + * is not defined) + */ + double getNumericalVariance(); + + /** + * Access the lower bound of the support. This method must return the same value as {@code + * inverseCumulativeProbability(0)}. In other words, this method must return + * + * <p><code>inf {x in Z | P(X <= x) > 0}</code>. + * + * @return lower bound of the support ({@code Integer.MIN_VALUE} for negative infinity) + */ + int getSupportLowerBound(); + + /** + * Access the upper bound of the support. This method must return the same value as {@code + * inverseCumulativeProbability(1)}. In other words, this method must return + * + * <p><code>inf {x in R | P(X <= x) = 1}</code>. + * + * @return upper bound of the support ({@code Integer.MAX_VALUE} for positive infinity) + */ + int getSupportUpperBound(); + + /** + * Use this method to get information about whether the support is connected, i.e. whether all + * integers between the lower and upper bound of the support are included in the support. + * + * @return whether the support is connected or not + */ + boolean isSupportConnected(); + + /** + * Reseed the random generator used to generate samples. + * + * @param seed the new seed + * @since 3.0 + */ + void reseedRandomGenerator(long seed); + + /** + * Generate a random value sampled from this distribution. + * + * @return a random value + * @since 3.0 + */ + int sample(); + + /** + * Generate a random sample from the distribution. + * + * @param sampleSize the number of random values to generate + * @return an array representing the random sample + * @throws org.apache.commons.math3.exception.NotStrictlyPositiveException if {@code sampleSize} + * is not positive + * @since 3.0 + */ + int[] sample(int sampleSize); +} |