com.rapidminer.tools.expression.internal.function.statistical.Binominal.java Source code

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Here is the source code for com.rapidminer.tools.expression.internal.function.statistical.Binominal.java

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/**
 * Copyright (C) 2001-2015 by RapidMiner and the contributors
 *
 * Complete list of developers available at our web site:
 *
 * http://rapidminer.com
 *
 * This program 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.
 *
 * This program 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 this program.
 * If not, see http://www.gnu.org/licenses/.
 */
package com.rapidminer.tools.expression.internal.function.statistical;

import org.apache.commons.math3.util.CombinatoricsUtils;

import com.rapidminer.tools.Ontology;
import com.rapidminer.tools.expression.ExpressionType;
import com.rapidminer.tools.expression.FunctionInputException;
import com.rapidminer.tools.expression.internal.function.Abstract2DoubleInputFunction;

/**
 *
 * A {@link Function} for binominal coefficents.
 *
 * @author David Arnu
 *
 */
public class Binominal extends Abstract2DoubleInputFunction {

    /**
     * Constructs a binominal function.
     */
    public Binominal() {
        super("statistical.binom", 2, Ontology.INTEGER);
    }

    @Override
    protected ExpressionType computeType(ExpressionType... inputTypes) {
        ExpressionType left = inputTypes[0];
        ExpressionType right = inputTypes[1];

        if (left == ExpressionType.INTEGER && right == ExpressionType.INTEGER) {
            return ExpressionType.INTEGER;
        } else {
            throw new FunctionInputException("expression_parser.function_wrong_type", getFunctionName(), "integer");
        }
    }

    @Override
    protected double compute(double value1, double value2) {

        // special case for handling missing values
        if (Double.isNaN(value1) || Double.isNaN(value2)) {
            return Double.NaN;
        }

        if (value1 < 0 || value2 < 0) {
            throw new FunctionInputException("expression_parser.function_non_negative", getFunctionName());
        }
        // This is the common definition for the case for k > n.
        if (value2 > value1) {
            return 0;
        } else {
            return CombinatoricsUtils.binomialCoefficientDouble((int) value1, (int) value2);
        }
    }

}