public static ISymbolicExpressionTree Prune(ISymbolicExpressionTree tree, ISymbolicClassificationModelCreator modelCreator,
SymbolicClassificationSolutionImpactValuesCalculator impactValuesCalculator, ISymbolicDataAnalysisExpressionTreeInterpreter interpreter,
IClassificationProblemData problemData, DoubleLimit estimationLimits, IEnumerable <int> rows,
double nodeImpactThreshold = 0.0, bool pruneOnlyZeroImpactNodes = false)
{
var clonedTree = (ISymbolicExpressionTree)tree.Clone();
var model = modelCreator.CreateSymbolicClassificationModel(clonedTree, interpreter, estimationLimits.Lower, estimationLimits.Upper);
var nodes = clonedTree.Root.GetSubtree(0).GetSubtree(0).IterateNodesPrefix().ToList();
double qualityForImpactsCalculation = double.NaN;
for (int i = 0; i < nodes.Count; ++i)
{
var node = nodes[i];
if (node is ConstantTreeNode)
{
continue;
}
double impactValue, replacementValue, newQualityForImpactsCalculation;
impactValuesCalculator.CalculateImpactAndReplacementValues(model, node, problemData, rows, out impactValue, out replacementValue, out newQualityForImpactsCalculation, qualityForImpactsCalculation);
if (pruneOnlyZeroImpactNodes && !impactValue.IsAlmost(0.0))
{
continue;
}
if (!pruneOnlyZeroImpactNodes && impactValue > nodeImpactThreshold)
{
continue;
}
var constantNode = (ConstantTreeNode)node.Grammar.GetSymbol("Constant").CreateTreeNode();
constantNode.Value = replacementValue;
ReplaceWithConstant(node, constantNode);
i += node.GetLength() - 1; // skip subtrees under the node that was folded
qualityForImpactsCalculation = newQualityForImpactsCalculation;
}
return(model.SymbolicExpressionTree);
}
public static double Calculate(ISymbolicDataAnalysisExpressionTreeInterpreter interpreter, ISymbolicExpressionTree tree, double lowerEstimationLimit, double upperEstimationLimit, IClassificationProblemData problemData,
IEnumerable <int> rows, bool applyLinearScaling, ISymbolicClassificationModelCreator modelCreator, double normalizedMeanSquaredErrorWeightingFactor, double falseNegativeRateWeightingFactor, double falsePositiveRateWeightingFactor)
{
var estimatedValues = interpreter.GetSymbolicExpressionTreeValues(tree, problemData.Dataset, rows);
var targetClassValues = problemData.Dataset.GetDoubleValues(problemData.TargetVariable, rows);
var boundedEstimatedValues = estimatedValues.LimitToRange(lowerEstimationLimit, upperEstimationLimit).ToArray();
OnlineCalculatorError errorState;
double nmse;
//calculate performance measures
string positiveClassName = problemData.PositiveClass;
double[] classValues, thresholds;
IEnumerable <double> estimatedClassValues = null;
ISymbolicDiscriminantFunctionClassificationModel m;
var model = modelCreator.CreateSymbolicClassificationModel(problemData.TargetVariable, tree, interpreter, lowerEstimationLimit, upperEstimationLimit);
if ((m = model as ISymbolicDiscriminantFunctionClassificationModel) != null)
{
m.ThresholdCalculator.Calculate(problemData, boundedEstimatedValues, targetClassValues, out classValues, out thresholds);
m.SetThresholdsAndClassValues(thresholds, classValues);
estimatedClassValues = m.GetEstimatedClassValues(boundedEstimatedValues);
}
else
{
model.RecalculateModelParameters(problemData, rows);
estimatedClassValues = model.GetEstimatedClassValues(problemData.Dataset, rows);
}
var performanceCalculator = new ClassificationPerformanceMeasuresCalculator(positiveClassName, problemData.GetClassValue(positiveClassName));
performanceCalculator.Calculate(targetClassValues, estimatedClassValues);
if (performanceCalculator.ErrorState != OnlineCalculatorError.None)
{
return(Double.NaN);
}
double falseNegativeRate = 1 - performanceCalculator.TruePositiveRate;
double falsePositiveRate = performanceCalculator.FalsePositiveRate;
if (applyLinearScaling)
{
throw new NotSupportedException("The Weighted Performance Measures Evaluator does not suppport linear scaling!");
}
nmse = OnlineNormalizedMeanSquaredErrorCalculator.Calculate(targetClassValues, boundedEstimatedValues, out errorState);
if (errorState != OnlineCalculatorError.None)
{
return(Double.NaN);
}
return(normalizedMeanSquaredErrorWeightingFactor * nmse + falseNegativeRateWeightingFactor * falseNegativeRate + falsePositiveRateWeightingFactor * falsePositiveRate);
}
public static ISymbolicExpressionTree Prune(ISymbolicExpressionTree tree, ISymbolicClassificationModelCreator modelCreator,
SymbolicClassificationSolutionImpactValuesCalculator impactValuesCalculator, ISymbolicDataAnalysisExpressionTreeInterpreter interpreter,
IClassificationProblemData problemData, DoubleLimit estimationLimits, IEnumerable<int> rows,
double nodeImpactThreshold = 0.0, bool pruneOnlyZeroImpactNodes = false) {
var clonedTree = (ISymbolicExpressionTree)tree.Clone();
var model = modelCreator.CreateSymbolicClassificationModel(problemData.TargetVariable, clonedTree, interpreter, estimationLimits.Lower, estimationLimits.Upper);
var nodes = clonedTree.Root.GetSubtree(0).GetSubtree(0).IterateNodesPrefix().ToList();
double qualityForImpactsCalculation = double.NaN;
for (int i = 0; i < nodes.Count; ++i) {
var node = nodes[i];
if (node is ConstantTreeNode) continue;
double impactValue, replacementValue, newQualityForImpactsCalculation;
impactValuesCalculator.CalculateImpactAndReplacementValues(model, node, problemData, rows, out impactValue, out replacementValue, out newQualityForImpactsCalculation, qualityForImpactsCalculation);
if (pruneOnlyZeroImpactNodes && !impactValue.IsAlmost(0.0)) continue;
if (!pruneOnlyZeroImpactNodes && impactValue > nodeImpactThreshold) continue;
var constantNode = (ConstantTreeNode)node.Grammar.GetSymbol("Constant").CreateTreeNode();
constantNode.Value = replacementValue;
ReplaceWithConstant(node, constantNode);
i += node.GetLength() - 1; // skip subtrees under the node that was folded
qualityForImpactsCalculation = newQualityForImpactsCalculation;
}
return model.SymbolicExpressionTree;
}
