/*
* RapidMiner
*
* Copyright (C) 2001-2008 by Rapid-I and the contributors
*
* Complete list of developers available at our web site:
*
* http://rapid-i.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.operator.preprocessing;
import java.util.List;
import com.rapidminer.example.Attribute;
import com.rapidminer.example.ExampleSet;
import com.rapidminer.example.set.SplittedExampleSet;
import com.rapidminer.operator.IOObject;
import com.rapidminer.operator.Operator;
import com.rapidminer.operator.OperatorDescription;
import com.rapidminer.operator.OperatorException;
import com.rapidminer.operator.UserError;
import com.rapidminer.parameter.ParameterType;
import com.rapidminer.parameter.ParameterTypeString;
/**
* <p>This operator creates a SplittedExampleSet from an arbitrary example set.
* The partitions of the resulting example set are created according to the
* values of the specified attribute. This works similar to the
* <code>GROUP BY</code> clause in SQL.</p>
*
* <p>Please note that the resulting example set is simply a splitted example
* set where no subset is selected. Following operators might decide to select
* one or several of the subsets, e.g. one of the aggregation operators.</p>
*
* @author Christian Bockermann, Ingo Mierswa
* @version $Id: GroupByOperator.java,v 1.6 2008/07/07 07:06:42 ingomierswa Exp $
*/
public class GroupByOperator extends Operator {
public final static String PARAMETER_ATTRIBUTE_NAME = "attribute_name";
public GroupByOperator(OperatorDescription desc) {
super(desc);
}
public IOObject[] apply() throws OperatorException {
ExampleSet exampleSet = getInput(ExampleSet.class);
Attribute attribute = exampleSet.getAttributes().get(this.getParameterAsString(PARAMETER_ATTRIBUTE_NAME));
if (attribute == null) {
throw new UserError(this, 111, this.getParameterAsString(PARAMETER_ATTRIBUTE_NAME));
}
if (!attribute.isNominal()) {
throw new UserError(this, 103, new Object[] { this.getParameterAsString(PARAMETER_ATTRIBUTE_NAME), "grouping by attribute." });
}
SplittedExampleSet grouped = SplittedExampleSet.splitByAttribute(exampleSet, attribute);
return new IOObject[] { grouped };
}
public Class<?>[] getInputClasses() {
return new Class[] { ExampleSet.class };
}
public Class<?>[] getOutputClasses() {
return new Class[] { SplittedExampleSet.class };
}
public List<ParameterType> getParameterTypes() {
List<ParameterType> types = super.getParameterTypes();
types.add(new ParameterTypeString(PARAMETER_ATTRIBUTE_NAME,
"Name of the attribute which is used to create partitions. If no such attribute is found in the input-exampleset or the attribute is not nominal or not an integer, execution will fail.",
false));
return types;
}
}