private static SymbolicExpressionTreeNode MirrorTree(RegressionNodeModel regressionNode, IDictionary <int, RegressionNodeModel> dict,
IDictionary <int, IReadOnlyList <int> > trainingLeafRows,
IDictionary <int, IReadOnlyList <int> > testLeafRows,
IntValue nextId, IDataset data, IReadOnlyList <int> trainingRows, IReadOnlyList <int> testRows)
{
if (regressionNode.IsLeaf)
{
var i = nextId.Value++;
dict.Add(i, regressionNode);
trainingLeafRows.Add(i, trainingRows);
testLeafRows.Add(i, testRows);
return(new SymbolicExpressionTreeNode(new TextSymbol("Model " + i + "\n(" + trainingRows.Count + "/" + testRows.Count + ")")));
}
var pftext = "\npf = " + regressionNode.PruningStrength.ToString("0.###");
var text = regressionNode.SplitAttribute + " <= " + regressionNode.SplitValue.ToString("0.###");
if (!double.IsNaN(regressionNode.PruningStrength))
{
text += pftext;
}
var textNode = new SymbolicExpressionTreeNode(new TextSymbol(text));
IReadOnlyList <int> lTrainingRows, rTrainingRows;
IReadOnlyList <int> lTestRows, rTestRows;
RegressionTreeUtilities.SplitRows(trainingRows, data, regressionNode.SplitAttribute, regressionNode.SplitValue, out lTrainingRows, out rTrainingRows);
RegressionTreeUtilities.SplitRows(testRows, data, regressionNode.SplitAttribute, regressionNode.SplitValue, out lTestRows, out rTestRows);
textNode.AddSubtree(MirrorTree(regressionNode.Left, dict, trainingLeafRows, testLeafRows, nextId, data, lTrainingRows, lTestRows));
textNode.AddSubtree(MirrorTree(regressionNode.Right, dict, trainingLeafRows, testLeafRows, nextId, data, rTrainingRows, rTestRows));
return(textNode);
}
private static void BuildPruningModel(RegressionNodeModel regressionNode, ILeafModel leaf, IReadOnlyList <int> trainingRows, IReadOnlyList <int> pruningRows, PruningState state, RegressionTreeParameters regressionTreeParams, CancellationToken cancellationToken)
{
//create regressionProblemdata from pruning data
var vars = regressionTreeParams.AllowedInputVariables.Concat(new[] { regressionTreeParams.TargetVariable }).ToArray();
var reducedData = new Dataset(vars, vars.Select(x => regressionTreeParams.Data.GetDoubleValues(x, pruningRows).ToList()));
var pd = new RegressionProblemData(reducedData, regressionTreeParams.AllowedInputVariables, regressionTreeParams.TargetVariable);
pd.TrainingPartition.Start = pd.TrainingPartition.End = pd.TestPartition.Start = 0;
pd.TestPartition.End = reducedData.Rows;
//build pruning model
int numModelParams;
var model = leaf.BuildModel(trainingRows, regressionTreeParams, cancellationToken, out numModelParams);
//record error and complexities
var rmsModel = model.CreateRegressionSolution(pd).TestRootMeanSquaredError;
state.pruningSizes.Add(regressionNode, pruningRows.Count);
state.modelErrors.Add(regressionNode, rmsModel);
state.modelComplexities.Add(regressionNode, numModelParams);
if (regressionNode.IsLeaf)
{
state.nodeComplexities[regressionNode] = state.modelComplexities[regressionNode];
}
else
{
state.nodeComplexities.Add(regressionNode, state.nodeComplexities[regressionNode.Left] + state.nodeComplexities[regressionNode.Right] + 1);
}
}
protected RegressionNodeModel(RegressionNodeModel original, Cloner cloner) : base(original, cloner)
{
IsLeaf = original.IsLeaf;
Model = cloner.Clone(original.Model);
SplitValue = original.SplitValue;
SplitAttribute = original.SplitAttribute;
Left = cloner.Clone(original.Left);
Right = cloner.Clone(original.Right);
Parent = cloner.Clone(original.Parent);
NumSamples = original.NumSamples;
}
public void BuildModel(IReadOnlyList <int> trainingRows, IReadOnlyList <int> pruningRows, IScope statescope, ResultCollection results, CancellationToken cancellationToken)
{
var regressionTreeParams = (RegressionTreeParameters)statescope.Variables[DecisionTreeRegression.RegressionTreeParameterVariableName].Value;
//start with one node
Root = RegressionNodeModel.CreateNode(regressionTreeParams.TargetVariable, regressionTreeParams);
//split into (overfitted tree)
regressionTreeParams.Splitter.Split(this, trainingRows, statescope, cancellationToken);
//prune
regressionTreeParams.Pruning.Prune(this, trainingRows, pruningRows, statescope, cancellationToken);
}
private static double SubtreeError(RegressionNodeModel regressionNode, IDictionary <RegressionNodeModel, int> pruningSizes,
IDictionary <RegressionNodeModel, double> modelErrors)
{
if (regressionNode.IsLeaf)
{
return(modelErrors[regressionNode]);
}
var errorL = SubtreeError(regressionNode.Left, pruningSizes, modelErrors);
var errorR = SubtreeError(regressionNode.Right, pruningSizes, modelErrors);
errorL = errorL * errorL * pruningSizes[regressionNode.Left];
errorR = errorR * errorR * pruningSizes[regressionNode.Right];
return(Math.Sqrt((errorR + errorL) / pruningSizes[regressionNode]));
}
private static void GetLeafDepths(RegressionNodeModel n, int depth, ICollection <int> res)
{
if (n == null)
{
return;
}
if (n.Left == null && n.Right == null)
{
res.Add(depth);
}
else
{
GetLeafDepths(n.Left, depth + 1, res);
GetLeafDepths(n.Right, depth + 1, res);
}
}
public ConfidenceRegressionNodeModel(RegressionNodeModel parent) : base(parent)
{
}
private static RegressionNodeModel CreateNode(RegressionNodeModel parent, RegressionTreeParameters regressionTreeParams)
{
return(regressionTreeParams.LeafModel.ProvidesConfidence ? new ConfidenceRegressionNodeModel(parent) : new RegressionNodeModel(parent));
}
private RegressionNodeModel(RegressionNodeModel parent) : this(parent.TargetVariable)
{
Parent = parent;
IsLeaf = true;
}
protected RegressionNodeTreeModel(RegressionNodeTreeModel original, Cloner cloner) : base(original, cloner)
{
Root = cloner.Clone(original.Root);
}
public static void Initialize(IScope stateScope)
{
var param = (RegressionTreeParameters)stateScope.Variables[DecisionTreeRegression.RegressionTreeParameterVariableName].Value;
stateScope.Variables.Add(new Variable(RootVariableName, RegressionNodeModel.CreateNode(param.TargetVariable, param)));
}
