#region License Information
/* HeuristicLab
* Copyright (C) 2002-2015 Heuristic and Evolutionary Algorithms Laboratory (HEAL)
* and the BEACON Center for the Study of Evolution in Action.
*
* This file is part of HeuristicLab.
*
* HeuristicLab is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* HeuristicLab 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with HeuristicLab. If not, see .
*/
#endregion
using System;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;
using System.Text;
using HeuristicLab.Common;
using HeuristicLab.Core;
using HeuristicLab.Persistence.Default.CompositeSerializers.Storable;
using HeuristicLab.Problems.DataAnalysis;
namespace HeuristicLab.Algorithms.DataAnalysis {
[StorableClass]
[Item("RegressionTreeModel", "Represents a decision tree for regression.")]
public sealed class RegressionTreeModel : NamedItem, IRegressionModel {
// trees are represented as a flat array
internal struct TreeNode {
public readonly static string NO_VARIABLE = string.Empty;
public TreeNode(string varName, double val, int leftIdx = -1, int rightIdx = -1)
: this() {
VarName = varName;
Val = val;
LeftIdx = leftIdx;
RightIdx = rightIdx;
}
public string VarName { get; private set; } // name of the variable for splitting or NO_VARIABLE if terminal node
public double Val { get; private set; } // threshold
public int LeftIdx { get; private set; }
public int RightIdx { get; private set; }
// necessary because the default implementation of GetHashCode for structs in .NET would only return the hashcode of val here
public override int GetHashCode() {
return LeftIdx ^ RightIdx ^ Val.GetHashCode();
}
// necessary because of GetHashCode override
public override bool Equals(object obj) {
if (obj is TreeNode) {
var other = (TreeNode)obj;
return Val.Equals(other.Val) &&
VarName.Equals(other.VarName) &&
LeftIdx.Equals(other.LeftIdx) &&
RightIdx.Equals(other.RightIdx);
} else {
return false;
}
}
}
[Storable]
private readonly TreeNode[] tree;
[StorableConstructor]
private RegressionTreeModel(bool serializing) : base(serializing) { }
// cloning ctor
private RegressionTreeModel(RegressionTreeModel original, Cloner cloner)
: base(original, cloner) {
this.tree = original.tree; // shallow clone, tree must be readonly
}
internal RegressionTreeModel(TreeNode[] tree)
: base("RegressionTreeModel", "Represents a decision tree for regression.") {
this.tree = tree;
}
private static double GetPredictionForRow(TreeNode[] t, int nodeIdx, IDataset ds, int row) {
var node = t[nodeIdx];
if (node.VarName == TreeNode.NO_VARIABLE)
return node.Val;
// TODO: many calls to GetDoubleValue are slow because of the dictionary lookup in Dataset (see ticket #2417)
else if (ds.GetDoubleValue(node.VarName, row) <= node.Val)
return GetPredictionForRow(t, node.LeftIdx, ds, row);
else
return GetPredictionForRow(t, node.RightIdx, ds, row);
}
public override IDeepCloneable Clone(Cloner cloner) {
return new RegressionTreeModel(this, cloner);
}
public IEnumerable GetEstimatedValues(IDataset ds, IEnumerable rows) {
return rows.Select(r => GetPredictionForRow(tree, 0, ds, r));
}
public IRegressionSolution CreateRegressionSolution(IRegressionProblemData problemData) {
return new RegressionSolution(this, new RegressionProblemData(problemData));
}
// mainly for debugging
public override string ToString() {
return TreeToString(0, "");
}
private string TreeToString(int idx, string part) {
var n = tree[idx];
if (n.VarName == TreeNode.NO_VARIABLE) {
return string.Format(CultureInfo.InvariantCulture, "{0} -> {1:F}{2}", part, n.Val, Environment.NewLine);
} else {
return
TreeToString(n.LeftIdx, string.Format(CultureInfo.InvariantCulture, "{0}{1}{2} <= {3:F}", part, string.IsNullOrEmpty(part) ? "" : " and ", n.VarName, n.Val))
+ TreeToString(n.RightIdx, string.Format(CultureInfo.InvariantCulture, "{0}{1}{2} > {3:F}", part, string.IsNullOrEmpty(part) ? "" : " and ", n.VarName, n.Val));
}
}
}
}