org.apache.solr.client.solrj.io.eval.PolyFitEvaluator.java Source code

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Here is the source code for org.apache.solr.client.solrj.io.eval.PolyFitEvaluator.java

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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.solr.client.solrj.io.eval;

import java.io.IOException;
import java.math.BigDecimal;
import java.util.List;
import java.util.ArrayList;

import org.apache.commons.math3.analysis.polynomials.PolynomialFunction;
import org.apache.commons.math3.fitting.PolynomialCurveFitter;

import org.apache.commons.math3.fitting.WeightedObservedPoints;
import org.apache.solr.client.solrj.io.stream.expr.StreamExpression;
import org.apache.solr.client.solrj.io.stream.expr.StreamFactory;

public class PolyFitEvaluator extends RecursiveNumericEvaluator implements ManyValueWorker {
    protected static final long serialVersionUID = 1L;

    public PolyFitEvaluator(StreamExpression expression, StreamFactory factory) throws IOException {
        super(expression, factory);
    }

    @Override
    public Object doWork(Object... objects) throws IOException {

        if (objects.length > 3) {
            throw new IOException("polyfit function takes a maximum of 3 arguments.");
        }

        Object first = objects[0];

        double[] x = null;
        double[] y = null;
        int degree = 3;

        if (objects.length == 1) {
            //Only the y values passed

            y = ((List) first).stream().mapToDouble(value -> ((BigDecimal) value).doubleValue()).toArray();
            x = new double[y.length];
            for (int i = 0; i < y.length; i++) {
                x[i] = i;
            }

        } else if (objects.length == 3) {
            // x, y and degree passed

            Object second = objects[1];
            x = ((List) first).stream().mapToDouble(value -> ((BigDecimal) value).doubleValue()).toArray();
            y = ((List) second).stream().mapToDouble(value -> ((BigDecimal) value).doubleValue()).toArray();
            degree = ((Number) objects[2]).intValue();
        } else if (objects.length == 2) {
            if (objects[1] instanceof List) {
                // x and y passed
                Object second = objects[1];
                x = ((List) first).stream().mapToDouble(value -> ((BigDecimal) value).doubleValue()).toArray();
                y = ((List) second).stream().mapToDouble(value -> ((BigDecimal) value).doubleValue()).toArray();
            } else {
                // y and degree passed
                y = ((List) first).stream().mapToDouble(value -> ((BigDecimal) value).doubleValue()).toArray();
                x = new double[y.length];
                for (int i = 0; i < y.length; i++) {
                    x[i] = i;
                }

                degree = ((Number) objects[1]).intValue();
            }
        }

        PolynomialCurveFitter curveFitter = PolynomialCurveFitter.create(degree);
        WeightedObservedPoints points = new WeightedObservedPoints();
        for (int i = 0; i < x.length; i++) {
            points.add(x[i], y[i]);
        }

        double[] coef = curveFitter.fit(points.toList());
        PolynomialFunction pf = new PolynomialFunction(coef);

        List list = new ArrayList();
        for (double xvalue : x) {
            double yvalue = pf.value(xvalue);
            list.add(yvalue);
        }

        return list;
    }
}