eu.crisis_economics.abm.algorithms.statistics.FloorInterpolator.java Source code

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Here is the source code for eu.crisis_economics.abm.algorithms.statistics.FloorInterpolator.java

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/*
 * This file is part of CRISIS, an economics simulator.
 * 
 * Copyright (C) 2015 Ross Richardson
 * Copyright (C) 2015 John Kieran Phillips
 *
 * CRISIS is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * CRISIS is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with CRISIS.  If not, see <http://www.gnu.org/licenses/>.
 */
package eu.crisis_economics.abm.algorithms.statistics;

import java.util.TreeMap;

import org.apache.commons.math3.analysis.UnivariateFunction;
import org.apache.commons.math3.analysis.interpolation.UnivariateInterpolator;
import org.apache.commons.math3.exception.DimensionMismatchException;
import org.apache.commons.math3.exception.MathIllegalArgumentException;

import com.google.common.base.Preconditions;

/**
  * A custom implementation of the {@link UnivariateInterpolator} interface.<br><br>
  * 
  * This implementation generates a {@link UnivariateFunction} {@code F} which
  * evaluates as follows: the value {@code F(t)} is taken to be {@code y[x[t]]}
  * where {@code x[t]} is the closest interpolation key less than, or equal to, 
  * {@code t}. {@code F} performs an interpolation by simply rounding down the
  * argument to the closest interpolation keypoint {@code x} not greater than 
  * {@code t}.
  * 
  * @author phillips
  */
public final class FloorInterpolator implements UnivariateInterpolator {

    public FloorInterpolator() {
    } // Stateless

    @Override
    public UnivariateFunction interpolate(final double[] x, final double[] y)
            throws MathIllegalArgumentException, DimensionMismatchException {
        Preconditions.checkNotNull(x, y);
        if (x.length != y.length)
            throw new DimensionMismatchException(x.length, y.length);
        final int seriesLength = x.length;
        if (seriesLength == 0)
            throw new IllegalArgumentException(
                    "FloorInterpolator.interpolate: input data is empty. Interpolation cannot continue.");
        final TreeMap<Double, Double> tree = new TreeMap<Double, Double>();
        for (int i = 0; i < seriesLength; ++i)
            tree.put(x[i], y[i]);
        final UnivariateFunction result = new UnivariateFunction() {
            @Override
            public double value(final double t) {
                if (t < x[0])
                    return y[0];
                else if (t > x[seriesLength - 1])
                    return y[seriesLength - 1];
                else
                    return tree.floorEntry(t).getValue();
            }
        };
        return result;
    }

    /**
      * Returns a brief description of this object. The exact details of the
      * string are subject to change, and should not be regarded as fixed.
      */
    @Override
    public String toString() {
        return "Floor Interpolator";
    }
}