private void run(double[][] inputs, int[] outputs)
{
// Initial argument check
DecisionTreeHelper.CheckArgs(tree, inputs, outputs);
// Reset the usage of all attributes
for (int i = 0; i < attributeUsageCount.Length; i++)
{
// a[i] has never been used
attributeUsageCount[i] = 0;
}
thresholds = new double[tree.Attributes.Count][];
var candidates = new List <double>(inputs.Length);
// 0. Create candidate split thresholds for each attribute
for (int i = 0; i < tree.Attributes.Count; i++)
{
if (tree.Attributes[i].Nature == DecisionVariableKind.Continuous)
{
double[] v = inputs.GetColumn(i);
int[] o = (int[])outputs.Clone();
IGrouping <double, int>[] sortedValueToClassesMapping =
v.
Select((value, index) => new KeyValuePair <double, int>(value, o[index])).
GroupBy(keyValuePair => keyValuePair.Key, keyValuePair => keyValuePair.Value).
OrderBy(keyValuePair => keyValuePair.Key).
ToArray();
for (int j = 0; j < sortedValueToClassesMapping.Length - 1; j++)
{
// Following the results by Fayyad and Irani (1992) (see footnote on Quinlan (1996)):
// "If all cases of adjacent values V[i] and V[i+1] belong to the same class,
// a threshold between them cannot lead to a partition that has the maximum value of
// the criterion." i.e no reason the add the threshold as a candidate
IGrouping <double, int> currentValueToClasses = sortedValueToClassesMapping[j];
IGrouping <double, int> nextValueToClasses = sortedValueToClassesMapping[j + 1];
double a = nextValueToClasses.Key;
double b = currentValueToClasses.Key;
if (a - b > Constants.DoubleEpsilon && currentValueToClasses.Union(nextValueToClasses).Count() > 1)
{
candidates.Add((currentValueToClasses.Key + nextValueToClasses.Key) / 2.0);
}
}
thresholds[i] = candidates.ToArray();
candidates.Clear();
}
}
// 1. Create a root node for the tree
tree.Root = new DecisionNode(tree);
// Recursively split the tree nodes
split(tree.Root, inputs, outputs, 0);
}
/// <summary>
/// Learns a model that can map the given inputs to the given outputs.
/// </summary>
///
/// <param name="x">The model inputs.</param>
/// <param name="y">The desired outputs associated with each <paramref name="x">inputs</paramref>.</param>
/// <param name="weights">The weight of importance for each input-output pair (if supported by the learning algorithm).</param>
///
/// <returns>A model that has learned how to produce <paramref name="y"/> given <paramref name="x"/>.</returns>
///
public DecisionTree Learn(int?[][] x, int[] y, double[] weights = null)
{
if (Model == null)
{
init(DecisionTreeHelper.Create(x, y, this.Attributes));
}
this.run(x.Apply((xi, i, j) => xi.HasValue ? (double)xi : Double.NaN), y, weights);
return(Model);
}
/// <summary>
/// Learns a model that can map the given inputs to the given outputs.
/// </summary>
///
/// <param name="x">The model inputs.</param>
/// <param name="y">The desired outputs associated with each <paramref name="x">inputs</paramref>.</param>
/// <param name="weights">The weight of importance for each input-output pair (if supported by the learning algorithm).</param>
///
/// <returns>A model that has learned how to produce <paramref name="y"/> given <paramref name="x"/>.</returns>
///
public DecisionTree Learn(double[][] x, int[] y, double[] weights = null)
{
if (Model == null)
{
init(DecisionTreeHelper.Create(x, y, this.Attributes));
}
this.run(x, y, weights);
return(Model);
}
/// <summary>
/// Learns a model that can map the given inputs to the given outputs.
/// </summary>
///
/// <param name="x">The model inputs.</param>
/// <param name="y">The desired outputs associated with each <paramref name="x">inputs</paramref>.</param>
/// <param name="weights">The weight of importance for each input-output pair (if supported by the learning algorithm).</param>
///
/// <returns>A model that has learned how to produce <paramref name="y"/> given <paramref name="x"/>.</returns>
///
public DecisionTree Learn(int[][] x, int[] y, double[] weights = null)
{
if (weights != null)
{
throw new ArgumentException(Accord.Properties.Resources.NotSupportedWeights, "weights");
}
if (Model == null)
{
init(DecisionTreeHelper.Create(x, y, this.Attributes));
}
this.run(x.ToDouble(), y, weights);
return(Model);
}
/// <summary>
/// Learns a model that can map the given inputs to the given outputs.
/// </summary>
///
/// <param name="x">The model inputs.</param>
/// <param name="y">The desired outputs associated with each <paramref name="x">inputs</paramref>.</param>
/// <param name="weights">The weight of importance for each input-output pair (if supported by the learning algorithm).</param>
///
/// <returns>A model that has learned how to produce <paramref name="y"/> given <paramref name="x"/>.</returns>
///
public DecisionTree Learn(int?[][] x, int[] y, double[] weights = null)
{
if (weights != null)
{
throw new ArgumentException(Accord.Properties.Resources.NotSupportedWeights, "weights");
}
if (Model == null)
{
init(DecisionTreeHelper.Create(x, y, this.Attributes));
}
this.run(x.Apply((xi, i, j) => xi.HasValue ? (double)xi : Double.NaN), y);
return(Model);
}
private void run(int[][] inputs, int[] outputs)
{
// Initial argument check
DecisionTreeHelper.CheckArgs(Model, inputs, outputs);
// Reset the usage of all attributes
for (int i = 0; i < AttributeUsageCount.Length; i++)
{
// a[i] has never been used
AttributeUsageCount[i] = 0;
}
// 1. Create a root node for the tree
this.Model.Root = new DecisionNode(Model);
// Recursively split the tree nodes
split(Model.Root, inputs, outputs, 0);
}
