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/*
* 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.math.random;
import java.io.IOException;
import java.io.File;
import java.net.URL;
import java.util.List;
import org.apache.commons.math.stat.descriptive.StatisticalSummary;
import org.apache.commons.math.stat.descriptive.SummaryStatistics;
/**
* Represents an <a href="http://random.mat.sbg.ac.at/~ste/dipl/node11.html">
* empirical probability distribution</a> -- a probability distribution derived
* from observed data without making any assumptions about the functional form
* of the population distribution that the data come from.<p>
* Implementations of this interface maintain data structures, called
* <i>distribution digests</i>, that describe empirical distributions and
* support the following operations: <ul>
* <li>loading the distribution from a file of observed data values</li>
* <li>dividing the input data into "bin ranges" and reporting bin frequency
* counts (data for histogram)</li>
* <li>reporting univariate statistics describing the full set of data values
* as well as the observations within each bin</li>
* <li>generating random values from the distribution</li>
* </ul>
* Applications can use <code>EmpiricalDistribution</code> implementations to
* build grouped frequency histograms representing the input data or to
* generate random values "like" those in the input file -- i.e., the values
* generated will follow the distribution of the values in the file.</p>
*
* @version $Revision: 817128 $ $Date: 2009-09-21 03:30:53 +0200 (lun. 21 sept. 2009) $
*/
public interface EmpiricalDistribution {
/**
* Computes the empirical distribution from the provided
* array of numbers.
*
* @param dataArray the data array
*/
void load(double[] dataArray);
/**
* Computes the empirical distribution from the input file.
*
* @param file the input file
* @throws IOException if an IO error occurs
*/
void load(File file) throws IOException;
/**
* Computes the empirical distribution using data read from a URL.
*
* @param url url of the input file
* @throws IOException if an IO error occurs
*/
void load(URL url) throws IOException;
/**
* Generates a random value from this distribution.
* <strong>Preconditions:</strong><ul>
* <li>the distribution must be loaded before invoking this method</li></ul>
* @return the random value.
*
* @throws IllegalStateException if the distribution has not been loaded
*/
double getNextValue() throws IllegalStateException;
/**
* Returns a
* {@link org.apache.commons.math.stat.descriptive.StatisticalSummary}
* describing this distribution.
* <strong>Preconditions:</strong><ul>
* <li>the distribution must be loaded before invoking this method</li>
* </ul>
*
* @return the sample statistics
* @throws IllegalStateException if the distribution has not been loaded
*/
StatisticalSummary getSampleStats() throws IllegalStateException;
/**
* Property indicating whether or not the distribution has been loaded.
*
* @return true if the distribution has been loaded
*/
boolean isLoaded();
/**
* Returns the number of bins.
*
* @return the number of bins
*/
int getBinCount();
/**
* Returns a list of
* {@link org.apache.commons.math.stat.descriptive.SummaryStatistics}
* containing statistics describing the values in each of the bins. The
* List is indexed on the bin number.
*
* @return List of bin statistics
*/
List<SummaryStatistics> getBinStats();
/**
* Returns the array of upper bounds for the bins. Bins are: <br/>
* [min,upperBounds[0]],(upperBounds[0],upperBounds[1]],...,
* (upperBounds[binCount-2], upperBounds[binCount-1] = max].
*
* @return array of bin upper bounds
*/
double[] getUpperBounds();
}
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