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);
}
private ModifiableDataset(ModifiableDataset original, Cloner cloner) : base(original, cloner)
{
var variables = variableValues.Keys.ToList();
foreach (var v in variables)
{
var type = GetVariableType(v);
if (type == typeof(DateTime))
{
variableValues[v] = GetDateTimeValues(v).ToList();
}
else if (type == typeof(double))
{
variableValues[v] = GetDoubleValues(v).ToList();
}
else if (type == typeof(string))
{
variableValues[v] = GetStringValues(v).ToList();
}
else
{
throw new ArgumentException("Unsupported type " + type + " for variable " + v);
}
}
}
private static double CalculateQualityForReplacement(
IClassificationModel model,
ModifiableDataset modifiableDataset,
string variableName,
IList originalValues,
IEnumerable <int> rows,
IList replacementValues,
IEnumerable <double> targetValues)
{
modifiableDataset.ReplaceVariable(variableName, replacementValues);
var discModel = model as IDiscriminantFunctionClassificationModel;
if (discModel != null)
{
var problemData = new ClassificationProblemData(modifiableDataset, modifiableDataset.VariableNames, model.TargetVariable);
discModel.RecalculateModelParameters(problemData, rows);
}
//mkommend: ToList is used on purpose to avoid lazy evaluation that could result in wrong estimates due to variable replacements
var estimates = model.GetEstimatedClassValues(modifiableDataset, rows).ToList();
var ret = CalculateQuality(targetValues, estimates);
modifiableDataset.ReplaceVariable(variableName, originalValues);
return(ret);
}
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);
}
private static IList GetReplacementValuesForDouble(ModifiableDataset modifiableDataset,
IEnumerable <int> rows,
List <double> originalValues,
ReplacementMethodEnum replacementMethod = ReplacementMethodEnum.Shuffle)
{
IRandom random = new FastRandom(31415);
List <double> replacementValues;
double replacementValue;
switch (replacementMethod)
{
case ReplacementMethodEnum.Median:
replacementValue = rows.Select(r => originalValues[r]).Median();
replacementValues = Enumerable.Repeat(replacementValue, modifiableDataset.Rows).ToList();
break;
case ReplacementMethodEnum.Average:
replacementValue = rows.Select(r => originalValues[r]).Average();
replacementValues = Enumerable.Repeat(replacementValue, modifiableDataset.Rows).ToList();
break;
case ReplacementMethodEnum.Shuffle:
// new var has same empirical distribution but the relation to y is broken
// prepare a complete column for the dataset
replacementValues = Enumerable.Repeat(double.NaN, 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;
case ReplacementMethodEnum.Noise:
var avg = rows.Select(r => originalValues[r]).Average();
var stdDev = rows.Select(r => originalValues[r]).StandardDeviation();
// prepare a complete column for the dataset
replacementValues = Enumerable.Repeat(double.NaN, modifiableDataset.Rows).ToList();
// update column values
foreach (var r in rows)
{
replacementValues[r] = NormalDistributedRandom.NextDouble(random, avg, stdDev);
}
break;
default:
throw new ArgumentException(string.Format("ReplacementMethod {0} cannot be handled.", replacementMethod));
}
return(replacementValues);
}
private static IEnumerable <double> EvaluateModelWithReplacedVariable(IRegressionModel model, string variable,
ModifiableDataset dataset, IEnumerable <int> rows, IEnumerable <string> replacementValues)
{
var originalValues = dataset.GetReadOnlyStringValues(variable).ToList();
dataset.ReplaceVariable(variable, replacementValues.ToList());
//mkommend: ToList is used on purpose to avoid lazy evaluation that could result in wrong estimates due to variable replacements
var estimates = model.GetEstimatedValues(dataset, rows).ToList();
dataset.ReplaceVariable(variable, originalValues);
return(estimates);
}
private static double CalculateQualityForReplacement(
IRegressionModel model,
ModifiableDataset modifiableDataset,
string variableName,
IList originalValues,
IEnumerable <int> rows,
IList replacementValues,
IEnumerable <double> targetValues)
{
modifiableDataset.ReplaceVariable(variableName, replacementValues);
//mkommend: ToList is used on purpose to avoid lazy evaluation that could result in wrong estimates due to variable replacements
var estimates = model.GetEstimatedValues(modifiableDataset, rows).ToList();
var ret = CalculateQuality(targetValues, estimates);
modifiableDataset.ReplaceVariable(variableName, originalValues);
return(ret);
}
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);
}
private static IEnumerable <double> EvaluateModelWithReplacedVariable(IRegressionModel model, string variable, ModifiableDataset dataset, IEnumerable <int> rows, ReplacementMethodEnum replacement = ReplacementMethodEnum.Median)
{
var originalValues = dataset.GetReadOnlyDoubleValues(variable).ToList();
double replacementValue;
List <double> replacementValues;
IRandom rand;
switch (replacement)
{
case ReplacementMethodEnum.Median:
replacementValue = rows.Select(r => originalValues[r]).Median();
replacementValues = Enumerable.Repeat(replacementValue, dataset.Rows).ToList();
break;
case ReplacementMethodEnum.Average:
replacementValue = rows.Select(r => originalValues[r]).Average();
replacementValues = Enumerable.Repeat(replacementValue, dataset.Rows).ToList();
break;
case ReplacementMethodEnum.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(double.NaN, 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;
case ReplacementMethodEnum.Noise:
var avg = rows.Select(r => originalValues[r]).Average();
var stdDev = rows.Select(r => originalValues[r]).StandardDeviation();
rand = new FastRandom(31415);
// prepare a complete column for the dataset
replacementValues = Enumerable.Repeat(double.NaN, dataset.Rows).ToList();
// update column values
foreach (var r in rows)
{
replacementValues[r] = NormalDistributedRandom.NextDouble(rand, avg, stdDev);
}
break;
default:
throw new ArgumentException(string.Format("ReplacementMethod {0} cannot be handled.", replacement));
}
return(EvaluateModelWithReplacedVariable(model, variable, dataset, rows, replacementValues));
}
private ModifiableDataset(ModifiableDataset original, Cloner cloner) : base(original, cloner)
{
variableNames = new List <string>(original.variableNames);
variableValues = CloneValues(original.variableValues);
}
private static IEnumerable <double> EvaluateModelWithReplacedVariable(IRegressionModel model, string variable, ModifiableDataset dataset, IEnumerable <int> rows, ReplacementMethodEnum replacement = ReplacementMethodEnum.Median)
{
var originalValues = dataset.GetReadOnlyDoubleValues(variable).ToList();
double replacementValue;
List <double> replacementValues;
IRandom rand;
switch (replacement)
{
case ReplacementMethodEnum.Median:
replacementValue = rows.Select(r => originalValues[r]).Median();
replacementValues = Enumerable.Repeat(replacementValue, dataset.Rows).ToList();
break;
case ReplacementMethodEnum.Average:
replacementValue = rows.Select(r => originalValues[r]).Average();
replacementValues = Enumerable.Repeat(replacementValue, dataset.Rows).ToList();
break;
case ReplacementMethodEnum.Shuffle:
// new var has same empirical distribution but the relation to y is broken
rand = new FastRandom(31415);
replacementValues = rows.Select(r => originalValues[r]).Shuffle(rand).ToList();
break;
case ReplacementMethodEnum.Noise:
var avg = rows.Select(r => originalValues[r]).Average();
var stdDev = rows.Select(r => originalValues[r]).StandardDeviation();
rand = new FastRandom(31415);
replacementValues = rows.Select(_ => NormalDistributedRandom.NextDouble(rand, avg, stdDev)).ToList();
break;
default:
throw new ArgumentException(string.Format("ReplacementMethod {0} cannot be handled.", replacement));
}
dataset.ReplaceVariable(variable, replacementValues);
//mkommend: ToList is used on purpose to avoid lazy evaluation that could result in wrong estimates due to variable replacements
var estimates = model.GetEstimatedValues(dataset, rows).ToList();
dataset.ReplaceVariable(variable, originalValues);
return(estimates);
}