emlab.util.TrendEstimator.java Source code

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Here is the source code for emlab.util.TrendEstimator.java

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/*******************************************************************************
 * Copyright 2012 the original author or authors.
 * 
 * Licensed 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 emlab.util;

import org.apache.commons.math.stat.regression.SimpleRegression;

public class TrendEstimator {

    public static double[] estimateLinearTrend(double[][] input, double[] predictionYears) {
        ;
        //Get logarithm of second trend
        SimpleRegression sr = new SimpleRegression();
        sr.addData(input);
        double result[] = new double[predictionYears.length];
        for (int i = 0; i < result.length; i++) {
            result[i] = sr.predict(predictionYears[i]);
        }
        return result;

    }

    public static double[] estimateGeometricTrend(double[][] input, double[] predictionYears) {
        //Get logarithm of second trend
        for (int i = 0; i < input.length; i++) {
            input[i][1] = Math.log(input[i][1]);
        }
        //input[1]=log;
        SimpleRegression sr = new SimpleRegression();
        sr.addData(input);
        double result[] = new double[predictionYears.length];
        for (int i = 0; i < result.length; i++) {
            result[i] = Math.exp(sr.predict(predictionYears[i]));
        }
        return result;

    }

}