private static IList GetReplacementValues(ModifiableDataset modifiableDataset,
string variableName,
IRegressionModel model,
IEnumerable <int> rows,
IEnumerable <double> targetValues,
out IList originalValues,
ReplacementMethodEnum replacementMethod = ReplacementMethodEnum.Shuffle,
FactorReplacementMethodEnum factorReplacementMethod = FactorReplacementMethodEnum.Best)
{
IList replacementValues = null;
if (modifiableDataset.VariableHasType <double>(variableName))
{
originalValues = modifiableDataset.GetReadOnlyDoubleValues(variableName).ToList();
replacementValues = GetReplacementValuesForDouble(modifiableDataset, rows, (List <double>)originalValues, replacementMethod);
}
else if (modifiableDataset.VariableHasType <string>(variableName))
{
originalValues = modifiableDataset.GetReadOnlyStringValues(variableName).ToList();
replacementValues = GetReplacementValuesForString(model, modifiableDataset, variableName, rows, (List <string>)originalValues, targetValues, factorReplacementMethod);
}
else
{
throw new NotSupportedException("Variable not supported");
}
return(replacementValues);
}
public static IEnumerable <Tuple <string, double> > CalculateImpacts(
IRegressionModel model,
IRegressionProblemData problemData,
IEnumerable <double> estimatedValues,
IEnumerable <int> rows,
ReplacementMethodEnum replacementMethod = ReplacementMethodEnum.Shuffle,
FactorReplacementMethodEnum factorReplacementMethod = FactorReplacementMethodEnum.Best)
{
//fholzing: try and catch in case a different dataset is loaded, otherwise statement is neglectable
var missingVariables = model.VariablesUsedForPrediction.Except(problemData.Dataset.VariableNames);
if (missingVariables.Any())
{
throw new InvalidOperationException(string.Format("Can not calculate variable impacts, because the model uses inputs missing in the dataset ({0})", string.Join(", ", missingVariables)));
}
IEnumerable <double> targetValues = problemData.Dataset.GetDoubleValues(problemData.TargetVariable, rows);
var originalQuality = CalculateQuality(targetValues, estimatedValues);
var impacts = new Dictionary <string, double>();
var inputvariables = new HashSet <string>(problemData.AllowedInputVariables.Union(model.VariablesUsedForPrediction));
var modifiableDataset = ((Dataset)(problemData.Dataset).Clone()).ToModifiable();
foreach (var inputVariable in inputvariables)
{
impacts[inputVariable] = CalculateImpact(inputVariable, model, problemData, modifiableDataset, rows, replacementMethod, factorReplacementMethod, targetValues, originalQuality);
}
return(impacts.Select(i => Tuple.Create(i.Key, i.Value)));
}
private static IList GetReplacementValuesForString(IRegressionModel model,
ModifiableDataset modifiableDataset,
string variableName,
IEnumerable <int> rows,
List <string> originalValues,
IEnumerable <double> targetValues,
FactorReplacementMethodEnum factorReplacementMethod = FactorReplacementMethodEnum.Shuffle)
{
List <string> replacementValues = null;
IRandom random = new FastRandom(31415);
switch (factorReplacementMethod)
{
case FactorReplacementMethodEnum.Best:
// try replacing with all possible values and find the best replacement value
var bestQuality = double.NegativeInfinity;
foreach (var repl in modifiableDataset.GetStringValues(variableName, rows).Distinct())
{
List <string> curReplacementValues = Enumerable.Repeat(repl, modifiableDataset.Rows).ToList();
//fholzing: this result could be used later on (theoretically), but is neglected for better readability/method consistency
var newValue = CalculateQualityForReplacement(model, modifiableDataset, variableName, originalValues, rows, curReplacementValues, targetValues);
var curQuality = newValue;
if (curQuality > bestQuality)
{
bestQuality = curQuality;
replacementValues = curReplacementValues;
}
}
break;
case FactorReplacementMethodEnum.Mode:
var mostCommonValue = rows.Select(r => originalValues[r])
.GroupBy(v => v)
.OrderByDescending(g => g.Count())
.First().Key;
replacementValues = Enumerable.Repeat(mostCommonValue, modifiableDataset.Rows).ToList();
break;
case FactorReplacementMethodEnum.Shuffle:
// new var has same empirical distribution but the relation to y is broken
// prepare a complete column for the dataset
replacementValues = Enumerable.Repeat(string.Empty, modifiableDataset.Rows).ToList();
// shuffle only the selected rows
var shuffledValues = rows.Select(r => originalValues[r]).Shuffle(random).ToList();
int i = 0;
// update column values
foreach (var r in rows)
{
replacementValues[r] = shuffledValues[i++];
}
break;
default:
throw new ArgumentException(string.Format("FactorReplacementMethod {0} cannot be handled.", factorReplacementMethod));
}
return(replacementValues);
}
public static IEnumerable <Tuple <string, double> > CalculateImpacts(
IRegressionSolution solution,
ReplacementMethodEnum replacementMethod = ReplacementMethodEnum.Shuffle,
FactorReplacementMethodEnum factorReplacementMethod = FactorReplacementMethodEnum.Best,
DataPartitionEnum dataPartition = DataPartitionEnum.Training)
{
IEnumerable <int> rows = GetPartitionRows(dataPartition, solution.ProblemData);
IEnumerable <double> estimatedValues = solution.GetEstimatedValues(rows);
return(CalculateImpacts(solution.Model, solution.ProblemData, estimatedValues, rows, replacementMethod, factorReplacementMethod));
}
public static IEnumerable <Tuple <string, double> > CalculateImpacts(
IClassificationSolution solution,
ReplacementMethodEnum replacementMethod = ReplacementMethodEnum.Shuffle,
FactorReplacementMethodEnum factorReplacementMethod = FactorReplacementMethodEnum.Best,
DataPartitionEnum dataPartition = DataPartitionEnum.Training)
{
IEnumerable <int> rows = GetPartitionRows(dataPartition, solution.ProblemData);
IEnumerable <double> estimatedClassValues = solution.GetEstimatedClassValues(rows);
var model = (IClassificationModel)solution.Model.Clone(); //mkommend: clone of model is necessary, because the thresholds for IDiscriminantClassificationModels are updated
return(CalculateImpacts(model, solution.ProblemData, estimatedClassValues, rows, replacementMethod, factorReplacementMethod));
}
private static IEnumerable <double> EvaluateModelWithReplacedVariable(
IRegressionModel model, string variable, ModifiableDataset dataset,
IEnumerable <int> rows,
FactorReplacementMethodEnum replacement = FactorReplacementMethodEnum.Shuffle)
{
var originalValues = dataset.GetReadOnlyStringValues(variable).ToList();
List <string> replacementValues;
IRandom rand;
switch (replacement)
{
case FactorReplacementMethodEnum.Mode:
var mostCommonValue = rows.Select(r => originalValues[r])
.GroupBy(v => v)
.OrderByDescending(g => g.Count())
.First().Key;
replacementValues = Enumerable.Repeat(mostCommonValue, dataset.Rows).ToList();
break;
case FactorReplacementMethodEnum.Shuffle:
// new var has same empirical distribution but the relation to y is broken
rand = new FastRandom(31415);
// prepare a complete column for the dataset
replacementValues = Enumerable.Repeat(string.Empty, dataset.Rows).ToList();
// shuffle only the selected rows
var shuffledValues = rows.Select(r => originalValues[r]).Shuffle(rand).ToList();
int i = 0;
// update column values
foreach (var r in rows)
{
replacementValues[r] = shuffledValues[i++];
}
break;
default:
throw new ArgumentException(string.Format("FactorReplacementMethod {0} cannot be handled.", replacement));
}
return(EvaluateModelWithReplacedVariable(model, variable, dataset, rows, replacementValues));
}
public static double CalculateImpact(string variableName,
IRegressionModel model,
IRegressionProblemData problemData,
ModifiableDataset modifiableDataset,
IEnumerable <int> rows,
ReplacementMethodEnum replacementMethod = ReplacementMethodEnum.Shuffle,
FactorReplacementMethodEnum factorReplacementMethod = FactorReplacementMethodEnum.Best,
IEnumerable <double> targetValues = null,
double quality = double.NaN)
{
if (!model.VariablesUsedForPrediction.Contains(variableName))
{
return(0.0);
}
if (!problemData.Dataset.VariableNames.Contains(variableName))
{
throw new InvalidOperationException(string.Format("Can not calculate variable impact, because the model uses inputs missing in the dataset ({0})", variableName));
}
if (targetValues == null)
{
targetValues = problemData.Dataset.GetDoubleValues(problemData.TargetVariable, rows);
}
if (quality == double.NaN)
{
quality = CalculateQuality(model.GetEstimatedValues(modifiableDataset, rows), targetValues);
}
IList originalValues = null;
IList replacementValues = GetReplacementValues(modifiableDataset, variableName, model, rows, targetValues, out originalValues, replacementMethod, factorReplacementMethod);
double newValue = CalculateQualityForReplacement(model, modifiableDataset, variableName, originalValues, rows, replacementValues, targetValues);
double impact = quality - newValue;
return(impact);
}
public static IEnumerable <Tuple <string, double> > CalculateImpacts(
IRegressionSolution solution,
DataPartitionEnum data = DataPartitionEnum.Training,
ReplacementMethodEnum replacementMethod = ReplacementMethodEnum.Median,
FactorReplacementMethodEnum factorReplacementMethod = FactorReplacementMethodEnum.Best)
{
var problemData = solution.ProblemData;
var dataset = problemData.Dataset;
IEnumerable <int> rows;
IEnumerable <double> targetValues;
double originalR2 = -1;
OnlineCalculatorError error;
switch (data)
{
case DataPartitionEnum.All:
rows = solution.ProblemData.AllIndices;
targetValues = problemData.TargetVariableValues.ToList();
originalR2 = OnlinePearsonsRCalculator.Calculate(problemData.TargetVariableValues, solution.EstimatedValues, out error);
if (error != OnlineCalculatorError.None)
{
throw new InvalidOperationException("Error during R² calculation.");
}
originalR2 = originalR2 * originalR2;
break;
case DataPartitionEnum.Training:
rows = problemData.TrainingIndices;
targetValues = problemData.TargetVariableTrainingValues.ToList();
originalR2 = solution.TrainingRSquared;
break;
case DataPartitionEnum.Test:
rows = problemData.TestIndices;
targetValues = problemData.TargetVariableTestValues.ToList();
originalR2 = solution.TestRSquared;
break;
default: throw new ArgumentException(string.Format("DataPartition {0} cannot be handled.", data));
}
var impacts = new Dictionary <string, double>();
var modifiableDataset = ((Dataset)dataset).ToModifiable();
var inputvariables = new HashSet <string>(problemData.AllowedInputVariables.Union(solution.Model.VariablesUsedForPrediction));
var allowedInputVariables = dataset.VariableNames.Where(v => inputvariables.Contains(v)).ToList();
// calculate impacts for double variables
foreach (var inputVariable in allowedInputVariables.Where(problemData.Dataset.VariableHasType <double>))
{
var newEstimates = EvaluateModelWithReplacedVariable(solution.Model, inputVariable, modifiableDataset, rows, replacementMethod);
var newR2 = OnlinePearsonsRCalculator.Calculate(targetValues, newEstimates, out error);
if (error != OnlineCalculatorError.None)
{
throw new InvalidOperationException("Error during R² calculation with replaced inputs.");
}
newR2 = newR2 * newR2;
var impact = originalR2 - newR2;
impacts[inputVariable] = impact;
}
// calculate impacts for string variables
foreach (var inputVariable in allowedInputVariables.Where(problemData.Dataset.VariableHasType <string>))
{
if (factorReplacementMethod == FactorReplacementMethodEnum.Best)
{
// try replacing with all possible values and find the best replacement value
var smallestImpact = double.PositiveInfinity;
foreach (var repl in problemData.Dataset.GetStringValues(inputVariable, rows).Distinct())
{
var newEstimates = EvaluateModelWithReplacedVariable(solution.Model, inputVariable, modifiableDataset, rows,
Enumerable.Repeat(repl, dataset.Rows));
var newR2 = OnlinePearsonsRCalculator.Calculate(targetValues, newEstimates, out error);
if (error != OnlineCalculatorError.None)
{
throw new InvalidOperationException("Error during R² calculation with replaced inputs.");
}
newR2 = newR2 * newR2;
var impact = originalR2 - newR2;
if (impact < smallestImpact)
{
smallestImpact = impact;
}
}
impacts[inputVariable] = smallestImpact;
}
else
{
// for replacement methods shuffle and mode
// calculate impacts for factor variables
var newEstimates = EvaluateModelWithReplacedVariable(solution.Model, inputVariable, modifiableDataset, rows,
factorReplacementMethod);
var newR2 = OnlinePearsonsRCalculator.Calculate(targetValues, newEstimates, out error);
if (error != OnlineCalculatorError.None)
{
throw new InvalidOperationException("Error during R² calculation with replaced inputs.");
}
newR2 = newR2 * newR2;
var impact = originalR2 - newR2;
impacts[inputVariable] = impact;
}
} // foreach
return(impacts.OrderByDescending(i => i.Value).Select(i => Tuple.Create(i.Key, i.Value)));
}
