org.jpmml.evaluator.functions.StandardDeviationFunction.java Source code

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Here is the source code for org.jpmml.evaluator.functions.StandardDeviationFunction.java

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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 <http://www.gnu.org/licenses/>.
 */
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.TypeCheckException;
import org.jpmml.evaluator.TypeUtil;

/**
 * Pseudo-declaration of function:
 * <pre>
 *   &lt;DefineFunction name="..." dataType="double"&gt;
 *     &lt;ParameterField name="values" dataType="collection of numbers"/&gt;
 *     &lt;ParameterField name="biasCorrected" dataType="boolean"/&gt; &lt;!-- Optional; defaults to false --&gt;
 *   &lt;/DefineFunction&gt;
 * </pre>
 *
 * @see StandardDeviation
 */
public class StandardDeviationFunction extends AbstractFunction {

    public StandardDeviationFunction() {
        this(StandardDeviationFunction.class.getName());
    }

    public StandardDeviationFunction(String name) {
        super(name);
    }

    @Override
    public FieldValue evaluate(List<FieldValue> arguments) {

        if (arguments.size() < 1 || arguments.size() > 2) {
            throw new FunctionException(getName(),
                    "Expected 1 or 2 arguments, but got " + arguments.size() + " arguments");
        } // End if

        if (arguments.contains(null)) {
            throw new FunctionException(getName(), "Missing arguments");
        }

        Object values = (arguments.get(0)).getValue();

        if (!(values instanceof Collection)) {
            throw new TypeCheckException(Collection.class, values);
        }

        Boolean biasCorrected = Boolean.FALSE;
        if (arguments.size() > 1) {
            biasCorrected = (arguments.get(1)).asBoolean();
        }

        Double result = evaluate((Collection<?>) 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();
    }
}