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source: trunk/sources/HeuristicLab.Problems.DataAnalysis/3.3/Symbolic/SimpleArithmeticExpressionEvaluator.cs @ 3253

Last change on this file since 3253 was 3253, checked in by gkronber, 13 years ago

Implemented basic framework for symbolic regression problems for HL 3.3. #938 (Data types and operators for regression problems)

File size: 3.1 KB
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1#region License Information
2/* HeuristicLab
3 * Copyright (C) 2002-2010 Heuristic and Evolutionary Algorithms Laboratory (HEAL)
4 *
5 * This file is part of HeuristicLab.
6 *
7 * HeuristicLab is free software: you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License as published by
9 * the Free Software Foundation, either version 3 of the License, or
10 * (at your option) any later version.
11 *
12 * HeuristicLab is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15 * GNU General Public License for more details.
16 *
17 * You should have received a copy of the GNU General Public License
18 * along with HeuristicLab. If not, see <http://www.gnu.org/licenses/>.
19 */
20#endregion
21
22using System;
23using HeuristicLab.Common;
24using HeuristicLab.Persistence.Default.CompositeSerializers.Storable;
25using HeuristicLab.Core;
26using System.Collections.Generic;
27using HeuristicLab.Encodings.SymbolicExpressionTreeEncoding;
28using HeuristicLab.Problems.DataAnalysis.Symbolic.Symbols;
29
30namespace HeuristicLab.Problems.DataAnalysis.Symbolic {
31  /// <summary>
32  /// Evaluates FunctionTrees recursively by interpretation of the function symbols in each node.
33  /// Simple unoptimized code, arithmetic expressions only.
34  /// Not thread-safe!
35  /// </summary>
36  [StorableClass]
37  [Item("SimpleArithmeticExpressionEvaluator", "Default evaluator for arithmetic symbolic expression trees.")]
38  public class SimpleArithmeticExpressionEvaluator : Item {
39    public IEnumerable<double> EstimatedValues(SymbolicExpressionTree tree, Dataset dataset, IEnumerable<int> rows) {
40      foreach (var row in rows) {
41        var estimatedValue = Evaluate(tree.Root.SubTrees[0], dataset, row);
42        if (double.IsNaN(estimatedValue) || double.IsInfinity(estimatedValue)) yield return 0.0;
43        else yield return estimatedValue;
44      }
45    }
46
47    private double Evaluate(SymbolicExpressionTreeNode node, Dataset dataset, int row) {
48      if (node.Symbol is HeuristicLab.Problems.DataAnalysis.Symbolic.Symbols.Variable) {
49        var variableTreeNode = node as VariableTreeNode;
50        return dataset[row, 1 /*dataset.VariableIndex(variableTreeNode.VariableName)*/] * 1.0; //variableTreeNode.Weight;
51      } else if (node.Symbol is Constant) {
52        return ((ConstantTreeNode)node).Value;
53      } else if (node.Symbol is Addition) {
54        return Evaluate(node.SubTrees[0], dataset, row) + Evaluate(node.SubTrees[1], dataset, row);
55      } else if (node.Symbol is Subtraction) {
56        return Evaluate(node.SubTrees[0], dataset, row) - Evaluate(node.SubTrees[1], dataset, row);
57      } else if (node.Symbol is Multiplication) {
58        return Evaluate(node.SubTrees[0], dataset, row) * Evaluate(node.SubTrees[1], dataset, row);
59      } else if (node.Symbol is Division) {
60        return Evaluate(node.SubTrees[0], dataset, row) / Evaluate(node.SubTrees[1], dataset, row);
61      } else {
62        throw new NotSupportedException("Tree contains unknown symbol: " + node.Symbol.Name);
63      }
64    }
65  }
66}
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