Source for org.jfree.formula.function.math.AverageFunction

   1: /**
   2:  * =========================================
   3:  * LibFormula : a free Java formula library
   4:  * =========================================
   5:  *
   6:  * Project Info:  http://reporting.pentaho.org/libformula/
   7:  *
   8:  * (C) Copyright 2006-2007, by Pentaho Corporation and Contributors.
   9:  *
  10:  * This library is free software; you can redistribute it and/or modify it under the terms
  11:  * of the GNU Lesser General Public License as published by the Free Software Foundation;
  12:  * either version 2.1 of the License, or (at your option) any later version.
  13:  *
  14:  * This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
  15:  * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
  16:  * See the GNU Lesser General Public License for more details.
  17:  *
  18:  * You should have received a copy of the GNU Lesser General Public License along with this
  19:  * library; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
  20:  * Boston, MA 02111-1307, USA.
  21:  *
  22:  * [Java is a trademark or registered trademark of Sun Microsystems, Inc.
  23:  * in the United States and other countries.]
  24:  *
  25:  *
  26:  * ------------
  27:  * $Id: AverageFunction.java,v 1.2 2007/05/08 09:47:09 taqua Exp $
  28:  * ------------
  29:  * (C) Copyright 2006-2007, by Pentaho Corporation.
  30:  */
  31: package org.jfree.formula.function.math;
  32: 
  33: import java.math.BigDecimal;
  34: 
  35: import org.jfree.formula.EvaluationException;
  36: import org.jfree.formula.FormulaContext;
  37: import org.jfree.formula.function.Function;
  38: import org.jfree.formula.function.ParameterCallback;
  39: import org.jfree.formula.lvalues.TypeValuePair;
  40: import org.jfree.formula.typing.coretypes.NumberType;
  41: 
  42: /**
  43:  * This function returns the average of the number sequence.
  44:  *
  45:  * @author Cedric Pronzato
  46:  */
  47: public class AverageFunction implements Function
  48: {
  49: 
  50:   public AverageFunction()
  51:   {
  52:   }
  53: 
  54:   public String getCanonicalName()
  55:   {
  56:     return "AVERAGE";
  57:   }
  58: 
  59:   public TypeValuePair evaluate(final FormulaContext context,
  60:                                 final ParameterCallback parameters)
  61:       throws EvaluationException
  62:   {
  63:     final SumFunction sumFunction = new SumFunction();
  64:     final TypeValuePair sum = sumFunction.evaluate(context, parameters);
  65: 
  66:     final Number n = context.getTypeRegistry().convertToNumber(sum.getType(), sum.getValue());
  67:     final BigDecimal divident = new BigDecimal(n.toString());
  68:     final BigDecimal divisor = new BigDecimal(parameters.getParameterCount());
  69:     final BigDecimal avg = divident.divide(divisor, BigDecimal.ROUND_HALF_UP);
  70: 
  71:     return new TypeValuePair(NumberType.GENERIC_NUMBER, avg);
  72:   }
  73: }