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Java example source code file (ListUnivariateImpl.java)

This example Java source code file (ListUnivariateImpl.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

arraylist, defaulttransformer, descriptivestatistics, listunivariateimpl, mathillegalargumentexception, numbertransformer, override, serializable, util

The ListUnivariateImpl.java Java example source code

/*
 * 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.stat.descriptive;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;

import org.apache.commons.math3.exception.MathIllegalArgumentException;
import org.apache.commons.math3.stat.descriptive.UnivariateStatistic;
import org.apache.commons.math3.stat.descriptive.DescriptiveStatistics;
import org.apache.commons.math3.util.DefaultTransformer;
import org.apache.commons.math3.util.FastMath;
import org.apache.commons.math3.util.NumberTransformer;

/**
 */
public class ListUnivariateImpl extends DescriptiveStatistics implements Serializable {

    /** Serializable version identifier */
    private static final long serialVersionUID = -8837442489133392138L;

    /**
     * Holds a reference to a list - GENERICs are going to make
     * our lives easier here as we could only accept List<Number>
     */
    protected List<Object> list;

    /** Number Transformer maps Objects to Number for us. */
    protected NumberTransformer transformer;

    /**
     * No argument Constructor
     */
    public ListUnivariateImpl(){
        this(new ArrayList<Object>());
    }

    /**
     * Construct a ListUnivariate with a specific List.
     * @param list The list that will back this DescriptiveStatistics
     */
    public ListUnivariateImpl(List<Object> list) {
        this(list, new DefaultTransformer());
    }

    /**
     * Construct a ListUnivariate with a specific List.
     * @param list The list that will back this DescriptiveStatistics
     * @param transformer the number transformer used to convert the list items.
     */
    public ListUnivariateImpl(List<Object> list, NumberTransformer transformer) {
        super();
        this.list = list;
        this.transformer = transformer;
    }

    /** {@inheritDoc} */
    @Override
    public double[] getValues() {

        int length = list.size();

        // If the window size is not INFINITE_WINDOW AND
        // the current list is larger that the window size, we need to
        // take into account only the last n elements of the list
        // as definied by windowSize

        final int wSize = getWindowSize();
        if (wSize != DescriptiveStatistics.INFINITE_WINDOW && wSize < list.size()) {
            length = list.size() - FastMath.max(0, list.size() - wSize);
        }

        // Create an array to hold all values
        double[] copiedArray = new double[length];

        for (int i = 0; i < copiedArray.length; i++) {
            copiedArray[i] = getElement(i);
        }
        return copiedArray;
    }

    /** {@inheritDoc} */
    @Override
    public double getElement(int index) {

        double value = Double.NaN;

        int calcIndex = index;

        final int wSize = getWindowSize();
        if (wSize != DescriptiveStatistics.INFINITE_WINDOW && wSize < list.size()) {
            calcIndex = (list.size() - wSize) + index;
        }


        try {
            value = transformer.transform(list.get(calcIndex));
        } catch (MathIllegalArgumentException e) {
            e.printStackTrace();
        }

        return value;
    }

    /** {@inheritDoc} */
    @Override
    public long getN() {
        int n = 0;

        final int wSize = getWindowSize();
        if (wSize != DescriptiveStatistics.INFINITE_WINDOW) {
            if (list.size() > wSize) {
                n = wSize;
            } else {
                n = list.size();
            }
        } else {
            n = list.size();
        }
        return n;
    }

    /** {@inheritDoc} */
    @Override
    public void addValue(double v) {
        list.add(Double.valueOf(v));
    }

    /**
     * Adds an object to this list.
     * @param o Object to add to the list
     */
    public void addObject(Object o) {
        list.add(o);
    }

    /**
     * Clears all statistics.
     * <p>
     * <strong>N.B.:  This method has the side effect of clearing the underlying list.
     */
    @Override
    public void clear() {
        list.clear();
    }

    /**
     * Apply the given statistic to this univariate collection.
     * @param stat the statistic to apply
     * @return the computed value of the statistic.
     */
    @Override
    public double apply(UnivariateStatistic stat) {
        double[] v = this.getValues();

        if (v != null) {
            return stat.evaluate(v, 0, v.length);
        }
        return Double.NaN;
    }

    /**
     * Access the number transformer.
     * @return the number transformer.
     */
    public NumberTransformer getTransformer() {
        return transformer;
    }

    /**
     * Modify the number transformer.
     * @param transformer the new number transformer.
     */
    public void setTransformer(NumberTransformer transformer) {
        this.transformer = transformer;
    }

    /** {@inheritDoc} */
    @Override
    public void setWindowSize(int windowSize) {
        super.setWindowSize(windowSize);
        //Discard elements from the front of the list if the windowSize is less than
        // the size of the list.
        int extra = list.size() - windowSize;
        for (int i = 0; i < extra; i++) {
            list.remove(0);
        }
    }

}

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