HoeffdingTreeRegressor

Hoeffding Tree regressor.

Parameters

• grace_period (int) – defaults to 200

  Number of instances a leaf should observe between split attempts.

• max_depth (int) – defaults to None

  The maximum depth a tree can reach. If None, the tree will grow indefinitely.

• delta (float) – defaults to 1e-07

  Significance level to calculate the Hoeffding bound. The significance level is given by 1 - delta. Values closer to zero imply longer split decision delays.

• tau (float) – defaults to 0.05

  Threshold below which a split will be forced to break ties.

• leaf_prediction (str) – defaults to adaptive

  Prediction mechanism used at leafs.
  - 'mean' - Target mean
  - 'model' - Uses the model defined in leaf_model
  - 'adaptive' - Chooses between 'mean' and 'model' dynamically
  

• leaf_model (base.Regressor) – defaults to None

  The regression model used to provide responses if leaf_prediction='model'. If not provided an instance of river.linear_model.LinearRegression with the default hyperparameters is used.

• model_selector_decay (float) – defaults to 0.95

  The exponential decaying factor applied to the learning models' squared errors, that are monitored if leaf_prediction='adaptive'. Must be between 0 and 1. The closer to 1, the more importance is going to be given to past observations. On the other hand, if its value approaches 0, the recent observed errors are going to have more influence on the final decision.

• nominal_attributes (list) – defaults to None

  List of Nominal attributes identifiers. If empty, then assume that all numeric attributes should be treated as continuous.

• splitter (river.tree.splitter.base.Splitter) – defaults to None

  The Splitter or Attribute Observer (AO) used to monitor the class statistics of numeric features and perform splits. Splitters are available in the tree.splitter module. Different splitters are available for classification and regression tasks. Classification and regression splitters can be distinguished by their property is_target_class. This is an advanced option. Special care must be taken when choosing different splitters. By default, tree.splitter.TEBSTSplitter is used if splitter is None.

• min_samples_split (int) – defaults to 5

  The minimum number of samples every branch resulting from a split candidate must have to be considered valid.

• binary_split (bool) – defaults to False

  If True, only allow binary splits.

• max_size (float) – defaults to 500.0

  The max size of the tree, in Megabytes (MB).

• memory_estimate_period (int) – defaults to 1000000

  Interval (number of processed instances) between memory consumption checks.

• stop_mem_management (bool) – defaults to False

  If True, stop growing as soon as memory limit is hit.

• remove_poor_attrs (bool) – defaults to False

  If True, disable poor attributes to reduce memory usage.

• merit_preprune (bool) – defaults to True

  If True, enable merit-based tree pre-pruning.

Attributes

• height

• leaf_prediction

  Return the prediction strategy used by the tree at its leaves.

• max_size

  Max allowed size tree can reach (in MB).

• n_active_leaves

• n_branches

• n_inactive_leaves

• n_leaves

• n_nodes

• split_criterion

  Return a string with the name of the split criterion being used by the tree.

• summary

  Collect metrics corresponding to the current status of the tree in a string buffer.

Examples

>>> from river import datasets
>>> from river import evaluate
>>> from river import metrics
>>> from river import tree
>>> from river import preprocessing

>>> dataset = datasets.TrumpApproval()

>>> model = (
...     preprocessing.StandardScaler() |
...     tree.HoeffdingTreeRegressor(
...         grace_period=100,
...         model_selector_decay=0.9
...     )
... )

>>> metric = metrics.MAE()

>>> evaluate.progressive_val_score(dataset, model, metric)
MAE: 0.781781

Methods

debug_one

Print an explanation of how x is predicted.

Parameters

• x (dict)

Returns

typing.Optional[str]: A representation of the path followed by the tree to predict x; None if

draw

Draw the tree using the graphviz library.

Since the tree is drawn without passing incoming samples, classification trees will show the majority class in their leaves, whereas regression trees will use the target mean.

Parameters

• max_depth (int) – defaults to None
  The maximum depth a tree can reach. If None, the tree will grow indefinitely.

learn_one

Train the tree model on sample x and corresponding target y.

Parameters

• x
• y
• sample_weight – defaults to 1.0

Returns

self

predict_one

Predict the target value using one of the leaf prediction strategies.

Parameters

• x

Returns

Predicted target value.

to_dataframe

Return a representation of the current tree structure organized in a pandas.DataFrame object.

In case the tree is empty or it only contains a single node (a leaf), None is returned.

Returns

df

Notes

The Hoeffding Tree Regressor (HTR) is an adaptation of the incremental tree algorithm of the same name for classification. Similarly to its classification counterpart, HTR uses the Hoeffding bound to control its split decisions. Differently from the classification algorithm, HTR relies on calculating the reduction of variance in the target space to decide among the split candidates. The smallest the variance at its leaf nodes, the more homogeneous the partitions are. At its leaf nodes, HTR fits either linear models or uses the target average as the predictor.