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/*
 * Copyright (c) 2014 Villu Ruusmann
 *
 * This file is part of JPMML-Evaluator
 *
 * JPMML-Evaluator is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * JPMML-Evaluator 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 Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with JPMML-Evaluator.  If not, see .
 */
package org.jpmml.evaluator.functions;

import java.util.Collection;
import java.util.List;

import org.apache.commons.math3.stat.descriptive.moment.StandardDeviation;
import org.dmg.pmml.DataType;
import org.jpmml.evaluator.FieldValue;
import org.jpmml.evaluator.FieldValueUtil;
import org.jpmml.evaluator.FunctionException;
import org.jpmml.evaluator.TypeUtil;

/**
 * 

* A Java UDF for calculating the standard deviation of a collection of values. *

* * Pseudo-declaration of function: *
 *   <DefineFunction name="..." dataType="double">
 *     <ParameterField name="values" dataType="collection of numbers"/>
 *     <ParameterField name="biasCorrected" dataType="boolean"/> <!-- Optional; defaults to false -->
 *   </DefineFunction>
 * 
* * @see StandardDeviation */ public class StandardDeviationFunction extends AbstractFunction { public StandardDeviationFunction(){ this(StandardDeviationFunction.class.getName()); } public StandardDeviationFunction(String name){ super(name); } @Override public FieldValue evaluate(List arguments){ if(arguments.size() < 1 || arguments.size() > 2){ throw new FunctionException(this, "Expected 1 or 2 arguments, but got " + arguments.size() + " arguments"); } // End if if(arguments.contains(null)){ throw new FunctionException(this, "Missing arguments"); } Collection values = FieldValueUtil.getValue(Collection.class, arguments.get(0)); Boolean biasCorrected = Boolean.FALSE; if(arguments.size() > 1){ biasCorrected = (arguments.get(1)).asBoolean(); } Double result = evaluate(values, biasCorrected); return FieldValueUtil.create(result); } static private Double evaluate(Collection values, boolean biasCorrected){ StandardDeviation statistic = new StandardDeviation(); statistic.setBiasCorrected(biasCorrected); for(Object value : values){ Double doubleValue = (Double)TypeUtil.parseOrCast(DataType.DOUBLE, value); statistic.increment(doubleValue); } return statistic.getResult(); } }




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