/*
* This program is free software; you can redistribute it and/or modify it under the
* terms of the GNU Lesser General Public License, version 2.1 as published by the Free Software
* Foundation.
*
* You should have received a copy of the GNU Lesser General Public License along with this
* program; if not, you can obtain a copy at http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html
* or from the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*
* 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 Lesser General Public License for more details.
*
* Copyright (c) 2006 - 2013 Pentaho Corporation and Contributors. All rights reserved.
*/
package org.pentaho.reporting.libraries.formula.function.math;
import org.pentaho.reporting.libraries.formula.EvaluationException;
import org.pentaho.reporting.libraries.formula.FormulaContext;
import org.pentaho.reporting.libraries.formula.LibFormulaErrorValue;
import org.pentaho.reporting.libraries.formula.function.Function;
import org.pentaho.reporting.libraries.formula.function.ParameterCallback;
import org.pentaho.reporting.libraries.formula.lvalues.TypeValuePair;
import org.pentaho.reporting.libraries.formula.typing.Type;
import org.pentaho.reporting.libraries.formula.typing.coretypes.NumberType;
import java.math.BigDecimal;
/**
* This function returns the acos of the value.
*
* @author ocke
*/
public class VarFunction implements Function {
public String getCanonicalName() {
return "VAR";
}
public TypeValuePair evaluate( FormulaContext context, ParameterCallback parameters ) throws EvaluationException {
final int parameterCount = parameters.getParameterCount();
if ( parameterCount < 2 ) {
throw EvaluationException.getInstance( LibFormulaErrorValue.ERROR_ARGUMENTS_VALUE );
}
double fSum = 0.0;
double vSum = 0.0;
double vMean = 0.0;
double nValCount = 0.0;
double[] values = new double[ parameterCount ];
for ( int i = 0; i < parameterCount; i++ ) {
final Type type1 = parameters.getType( i );
final Object value1 = parameters.getValue( i );
final Number result = context.getTypeRegistry().convertToNumber( type1, value1 );
if ( result == null ) {
throw EvaluationException.getInstance( LibFormulaErrorValue.ERROR_INVALID_ARGUMENT_VALUE );
}
final double d = result.doubleValue();
fSum += d;
values[ i ] = d;
nValCount++;
}
vMean = fSum / nValCount;
for ( int i = 0; i < nValCount; i++ ) {
vSum += ( values[ i ] - vMean ) * ( values[ i ] - vMean );
}
return new TypeValuePair( NumberType.GENERIC_NUMBER, new BigDecimal( vSum / ( nValCount - 1.0 ) ) );
}
}