Class: SVMKit::Tree::DecisionTreeClassifier

Inherits:
Object
  • Object
show all
Includes:
Base::BaseEstimator, Base::Classifier
Defined in:
lib/svmkit/tree/decision_tree_classifier.rb

Overview

DecisionTreeClassifier is a class that implements decision tree for classification.

Examples:

estimator =
  SVMKit::Tree::DecisionTreeClassifier.new(
    criterion: 'gini', max_depth: 3, max_leaf_nodes: 10, min_samples_leaf: 5, random_seed: 1)
estimator.fit(training_samples, traininig_labels)
results = estimator.predict(testing_samples)

Instance Attribute Summary collapse

Attributes included from Base::BaseEstimator

#params

Instance Method Summary collapse

Methods included from Base::Classifier

#score

Constructor Details

#initialize(criterion: 'gini', max_depth: nil, max_leaf_nodes: nil, min_samples_leaf: 1, max_features: nil, random_seed: nil) ⇒ DecisionTreeClassifier

Create a new classifier with decision tree algorithm.

Parameters:

  • criterion (String) (defaults to: 'gini') —

    The function to evalue spliting point. Supported criteria are ‘gini’ and ‘entropy’.

  • max_depth (Integer) (defaults to: nil) —

    The maximum depth of the tree. If nil is given, decision tree grows without concern for depth.

  • max_leaf_nodes (Integer) (defaults to: nil) —

    The maximum number of leaves on decision tree. If nil is given, number of leaves is not limited.

  • min_samples_leaf (Integer) (defaults to: 1) —

    The minimum number of samples at a leaf node.

  • max_features (Integer) (defaults to: nil) —

    The number of features to consider when searching optimal split point. If nil is given, split process considers all features.

  • random_seed (Integer) (defaults to: nil) —

    The seed value using to initialize the random generator. It is used to randomly determine the order of features when deciding spliting point.



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# File 'lib/svmkit/tree/decision_tree_classifier.rb', line 55

def initialize(criterion: 'gini', max_depth: nil, max_leaf_nodes: nil, min_samples_leaf: 1, max_features: nil,
               random_seed: nil)
  @params = {}
  @params[:criterion] = criterion
  @params[:max_depth] = max_depth
  @params[:max_leaf_nodes] = max_leaf_nodes
  @params[:min_samples_leaf] = min_samples_leaf
  @params[:max_features] = max_features
  @params[:random_seed] = random_seed
  @params[:random_seed] ||= srand
  @rng = Random.new(@params[:random_seed])
  @tree = nil
  @classes = nil
  @feature_importances = nil
  @n_leaves = nil
  @leaf_labels = nil
end

Instance Attribute Details

#classes ⇒ Numo::Int32 (readonly)

Return the class labels.

Returns:

  • (Numo::Int32) —

    (size: n_classes)



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# File 'lib/svmkit/tree/decision_tree_classifier.rb', line 25

def classes
  @classes
end

#feature_importances ⇒ Numo::DFloat (readonly)

Return the importance for each feature.

Returns:

  • (Numo::DFloat) —

    (size: n_features)



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# File 'lib/svmkit/tree/decision_tree_classifier.rb', line 29

def feature_importances
  @feature_importances
end

#leaf_labels ⇒ Numo::Int32 (readonly)

Return the labels assigned each leaf.

Returns:

  • (Numo::Int32) —

    (size: n_leafs)



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# File 'lib/svmkit/tree/decision_tree_classifier.rb', line 41

def leaf_labels
  @leaf_labels
end

#rng ⇒ Random (readonly)

Return the random generator for performing random sampling in the Pegasos algorithm.

Returns:

  • (Random) 


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# File 'lib/svmkit/tree/decision_tree_classifier.rb', line 37

def rng
  @rng
end

#tree ⇒ OpenStruct (readonly)

Return the learned tree.

Returns:

  • (OpenStruct) 


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# File 'lib/svmkit/tree/decision_tree_classifier.rb', line 33

def tree
  @tree
end

Instance Method Details

#apply(x) ⇒ Numo::Int32

Return the index of the leaf that each sample reached.

Parameters:

  • x (Numo::DFloat) —

    (shape: [n_samples, n_features]) The samples to predict the labels.

Returns:

  • (Numo::Int32) —

    (shape: [n_samples]) Leaf index for sample.



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# File 'lib/svmkit/tree/decision_tree_classifier.rb', line 109

def apply(x)
  Numo::Int32[*(Array.new(x.shape[0]) { |n| apply_at_node(@tree, x[n, true]) })]
end

#fit(x, y) ⇒ DecisionTreeClassifier

Fit the model with given training data.

Parameters:

  • x (Numo::DFloat) —

    (shape: [n_samples, n_features]) The training data to be used for fitting the model.

  • y (Numo::Int32) —

    (shape: [n_samples]) The labels to be used for fitting the model.

Returns:



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# File 'lib/svmkit/tree/decision_tree_classifier.rb', line 78

def fit(x, y)
  n_samples, n_features = x.shape
  @params[:max_features] = n_features unless @params[:max_features].is_a?(Integer)
  @params[:max_features] = [[1, @params[:max_features]].max, n_features].min
  @classes = Numo::Int32.asarray(y.to_a.uniq.sort)
  build_tree(x, y)
  eval_importance(n_samples, n_features)
  self
end

#marshal_dump ⇒ Hash

Dump marshal data.

Returns:

  • (Hash) —

    The marshal data about DecisionTreeClassifier



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# File 'lib/svmkit/tree/decision_tree_classifier.rb', line 115

def marshal_dump
  { params: @params, classes: @classes, tree: @tree,
    feature_importances: @feature_importances, leaf_labels: @leaf_labels,
    rng: @rng }
end

#marshal_load(obj) ⇒ nil

Load marshal data.

Returns:

  • (nil) 


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# File 'lib/svmkit/tree/decision_tree_classifier.rb', line 123

def marshal_load(obj)
  @params = obj[:params]
  @classes = obj[:classes]
  @tree = obj[:tree]
  @feature_importances = obj[:feature_importances]
  @leaf_labels = obj[:leaf_labels]
  @rng = obj[:rng]
  nil
end

#predict(x) ⇒ Numo::Int32

Predict class labels for samples.

Parameters:

  • x (Numo::DFloat) —

    (shape: [n_samples, n_features]) The samples to predict the labels.

Returns:

  • (Numo::Int32) —

    (shape: [n_samples]) Predicted class label per sample.



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# File 'lib/svmkit/tree/decision_tree_classifier.rb', line 92

def predict(x)
  @leaf_labels[apply(x)]
end

#predict_proba(x) ⇒ Numo::DFloat

Predict probability for samples.

Parameters:

  • x (Numo::DFloat) —

    (shape: [n_samples, n_features]) The samples to predict the probailities.

Returns:

  • (Numo::DFloat) —

    (shape: [n_samples, n_classes]) Predicted probability of each class per sample.



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# File 'lib/svmkit/tree/decision_tree_classifier.rb', line 100

def predict_proba(x)
  probs = Numo::DFloat[*(Array.new(x.shape[0]) { |n| predict_at_node(@tree, x[n, true]) })]
  probs[true, @classes]
end