DecisionTreeDiscretiser

class feature_engine.discretisation.DecisionTreeDiscretiser(variables=None, cv=3, scoring='neg_mean_squared_error', param_grid=None, regression=True, random_state=None)[source]

The DecisionTreeDiscretiser() replaces numerical variables by discrete, i.e., finite variables, which values are the predictions of a decision tree.

The method is inspired by the following article from the winners of the KDD 2009 competition: http://www.mtome.com/Publications/CiML/CiML-v3-book.pdf

The DecisionTreeDiscretiser() trains a decision tree per variable. Then, it transforms the variables, with predictions of the decision tree.

The DecisionTreeDiscretiser() works only with numerical variables. A list of variables to transform can be indicated. Alternatively, the discretiser will automatically select all numerical variables.

More details in the User Guide.

Parameters
variables: list, default=None

The list of numerical variables to transform. If None, the transformer will automatically find and select all numerical variables.

cv: int, cross-validation generator or an iterable, default=3

Determines the cross-validation splitting strategy. Possible inputs for cv are:

For int/None inputs, if the estimator is a classifier and y is either binary or multiclass, StratifiedKFold is used. In all other cases, KFold is used. These splitters are instantiated with shuffle=False so the splits will be the same across calls. For more details check Scikit-learn’s cross_validate’s documentation.

scoring: str, default=’neg_mean_squared_error’

Desired metric to optimise the performance of the tree. Comes from sklearn.metrics. See the DecisionTreeRegressor or DecisionTreeClassifier model evaluation documentation for more options: https://scikit-learn.org/stable/modules/model_evaluation.html

param_grid: dictionary, default=None

The hyperparameters for the decision tree to test with a grid search. The param_grid can contain any of the permitted hyperparameters for Scikit-learn’s DecisionTreeRegressor() or DecisionTreeClassifier(). If None, then param_grid will optimise the ‘max_depth’ over [1, 2, 3, 4].

regression: boolean, default=True

Indicates whether the discretiser should train a regression or a classification decision tree.

random_stateint, default=None

The random_state to initialise the training of the decision tree. It is one of the parameters of the Scikit-learn’s DecisionTreeRegressor() or DecisionTreeClassifier(). For reproducibility it is recommended to set the random_state to an integer.

Attributes
binner_dict_:

Dictionary containing the fitted tree per variable.

scores_dict_:

Dictionary with the score of the best decision tree per variable.

variables_:

The group of variables that will be transformed.

feature_names_in_:

List with the names of features seen during fit.

n_features_in_:

The number of features in the train set used in fit.

See also

sklearn.tree.DecisionTreeClassifier
sklearn.tree.DecisionTreeRegressor

References

1

Niculescu-Mizil, et al. “Winning the KDD Cup Orange Challenge with Ensemble Selection”. JMLR: Workshop and Conference Proceedings 7: 23-34. KDD 2009 http://proceedings.mlr.press/v7/niculescu09/niculescu09.pdf

Methods

fit:

Fit a decision tree per variable.

fit_transform:

Fit to data, then transform it.

get_feature_names_out:

Get output feature names for transformation.

get_params:

Get parameters for this estimator.

set_params:

Set the parameters of this estimator.

transform:

Replace continuous variable values by the predictions of the decision tree.

fit(X, y)[source]

Fit one decision tree per variable to discretize with cross-validation and grid-search for hyperparameters.

Parameters
X: pandas dataframe of shape = [n_samples, n_features]

The training dataset. Can be the entire dataframe, not just the variables to be transformed.

y: pandas series.

Target variable. Required to train the decision tree.

fit_transform(X, y=None, **fit_params)[source]

Fit to data, then transform it.

Fits transformer to X and y with optional parameters fit_params and returns a transformed version of X.

Parameters
Xarray-like of shape (n_samples, n_features)

Input samples.

yarray-like of shape (n_samples,) or (n_samples, n_outputs), default=None

Target values (None for unsupervised transformations).

**fit_paramsdict

Additional fit parameters.

Returns
X_newndarray array of shape (n_samples, n_features_new)

Transformed array.

get_feature_names_out(input_features=None)[source]

Get output feature names for transformation.

Parameters
input_features: str, list, default=None

If None, then the names of all the variables in the transformed dataset is returned. If list with feature names, the features in the list will be returned. This parameter exists mostly for compatibility with the Scikit-learn Pipeline.

Returns
feature_names_out: list

The feature names.

:rtype:py:class:~typing.List[Union[str, int]]
get_params(deep=True)[source]

Get parameters for this estimator.

Parameters
deepbool, default=True

If True, will return the parameters for this estimator and contained subobjects that are estimators.

Returns
paramsdict

Parameter names mapped to their values.

set_params(**params)[source]

Set the parameters of this estimator.

The method works on simple estimators as well as on nested objects (such as Pipeline). The latter have parameters of the form <component>__<parameter> so that it’s possible to update each component of a nested object.

Parameters
**paramsdict

Estimator parameters.

Returns
selfestimator instance

Estimator instance.

transform(X)[source]

Replaces original variable values with the predictions of the tree. The decision tree predictions are finite, aka, discrete.

Parameters
X: pandas dataframe of shape = [n_samples, n_features]

The input samples.

Returns
X_new: pandas dataframe of shape = [n_samples, n_features]

The dataframe with transformed variables.

:rtype:py:class:~pandas.core.frame.DataFrame