Boosting for classification

For each incoming observation, each model's learn_one method is called k times where k is sampled from a Poisson distribution of parameter lambda. The lambda parameter is updated when the weaks learners fit successively the same observation.

## Parameters¶

• model (base.Classifier)

The classifier to boost.

• n_models – defaults to 10

The number of models in the ensemble.

• seed (int) – defaults to None

Random number generator seed for reproducibility.

## Attributes¶

• wrong_weight (collections.defaultdict)

Number of times a model has made a mistake when making predictions.

• correct_weight (collections.defaultdict)

Number of times a model has predicted the right label when making predictions.

## Examples¶

In the following example three tree classifiers are boosted together. The performance is slightly better than when using a single tree.

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

>>> dataset = datasets.Phishing()

>>> metric = metrics.LogLoss()

>>> model = ensemble.AdaBoostClassifier(
...     model=(
...         tree.HoeffdingTreeClassifier(
...             split_criterion='gini',
...             split_confidence=1e-5,
...             grace_period=2000
...         )
...     ),
...     n_models=5,
...     seed=42
... )

>>> evaluate.progressive_val_score(dataset, model, metric)
LogLoss: 0.37111

>>> print(model)


## Methods¶

clone

Return a fresh estimator with the same parameters.

The clone has the same parameters but has not been updated with any data. This works by looking at the parameters from the class signature. Each parameter is either - recursively cloned if it's a River classes. - deep-copied via copy.deepcopy if not. If the calling object is stochastic (i.e. it accepts a seed parameter) and has not been seeded, then the clone will not be idempotent. Indeed, this method's purpose if simply to return a new instance with the same input parameters.

learn_one

Update the model with a set of features x and a label y.

Parameters

• x
• y

Returns

self

predict_many

Predict the labels of a DataFrame X.

Parameters

• X (pandas.core.frame.DataFrame)

Returns

Series: Series of predicted labels.

predict_one

Predict the label of a set of features x.

Parameters

• x (dict)

Returns

typing.Union[bool, str, int]: The predicted label.

predict_proba_many

Predict the labels of a DataFrame X.

Parameters

• X (pandas.core.frame.DataFrame)

Returns

DataFrame: DataFrame that associate probabilities which each label as columns.

predict_proba_one

Predict the probability of each label for a dictionary of features x.

Parameters

• x

Returns

A dictionary that associates a probability which each label.