decision_tree_classifier.py

# Copyright 2019 IBM Corporation
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

import sklearn.tree.tree
import lale.docstrings
import lale.operators

_hyperparams_schema = {
    '$schema': 'http://json-schema.org/draft-04/schema#',
    'description': 'A decision tree classifier.',
    'allOf': [{
        'type': 'object',
        'required': ['class_weight'],
        'relevantToOptimizer': ['criterion', 'splitter', 'max_depth', 'min_samples_split', 'min_samples_leaf', 'max_features'],
        'additionalProperties': False,
        'properties': {
            'criterion': {
                'enum': ['gini', 'entropy'],
                'default': 'gini',
                'description': 'The function to measure the quality of a split. Supported criteria are'},
            'splitter': {
                'enum': ['best', 'random'],
                'default': 'best',
                'description': 'The strategy used to choose the split at each node. Supported'},
            'max_depth': {
                'anyOf': [{
                    'type': 'integer',
                    'minimumForOptimizer': 3,
                    'maximumForOptimizer': 5}, {
                    'enum': [None]}],
                'default': None,
                'description': 'The maximum depth of the tree. If None, then nodes are expanded until'},
            'min_samples_split': {
                'anyOf': [{
                    'type': 'integer',
                    'minimumForOptimizer': 2,
                    'maximumForOptimizer': 20,
                    'distribution': 'uniform'}, {
                    'type': 'number',
                    'minimumForOptimizer': 0.01,
                    'maximumForOptimizer': 0.5}],
                'default': 2,
                'description': 'The minimum number of samples required to split an internal node:'},
            'min_samples_leaf': {
                'anyOf': [{
                    'type': 'integer',
                    'minimumForOptimizer': 1,
                    'maximumForOptimizer': 20,
                    'distribution': 'uniform'}, {
                    'type': 'number',
                    'minimumForOptimizer': 0.01,
                    'maximumForOptimizer': 0.5}],
                'default': 1,
                'description': 'The minimum number of samples required to be at a leaf node.'},
            'min_weight_fraction_leaf': {
                'type': 'number',
                'default': 0.0,
                'description': 'The minimum weighted fraction of the sum total of weights (of all'},
            'max_features': {
                'anyOf': [{
                    'type': 'integer',
                    'forOptimizer': False}, {
                    'type': 'number',
                    'minimum': 0.0,
                    'exclusiveMinimum': True,
                    'minimumForOptimizer': 0.0,
                    'maximumForOptimizer': 1.0,
                    'distribution': 'uniform'}, {
                    'enum': ['auto', 'sqrt', 'log2', None]}],
                'default': None,
                'description': 'The number of features to consider when looking for the best split:'},
            'random_state': {
                'anyOf': [{
                    'type': 'integer'}, {
                    'type': 'object'}, {
                    'enum': [None]}],
                'default': None,
                'description': 'If int, random_state is the seed used by the random number generator;'},
            'max_leaf_nodes': {
                'anyOf': [{
                    'type': 'integer'}, {
                    'enum': [None]}],
                'default': None,
                'description': 'Grow a tree with ``max_leaf_nodes`` in best-first fashion.'},
            'min_impurity_decrease': {
                'type': 'number',
                'default': 0.0,
                'description': 'A node will be split if this split induces a decrease of the impurity'},
            'min_impurity_split': {
                'anyOf':[
                {'type': 'number'},{
                    'enum': [None]
                }],
                'default': None,
                'description': 'Threshold for early stopping in tree growth. A node will split'},
            'class_weight': {
                'anyOf': [{
                    'type': 'object'}, #dict, list of dicts, 
                    {'enum': ['balanced', 'balanced_subsample', None]}],
                'description': 'Weights associated with classes in the form ``{class_label: weight}``.',
                'default': None},
            'presort': {
                'type': 'boolean',
                'default': False,
                'description': 'Whether to presort the data to speed up the finding of best splits in'},
        }}]
}

_input_fit_schema = {
    '$schema': 'http://json-schema.org/draft-04/schema#',
    'description': 'Build a decision tree classifier from the training set (X, y).',
    'required': ['X', 'y'],
    'type': 'object',
    'properties': {
        'X': {
            'anyOf': [{
                'type': 'array',
                'items': {
                    'type': 'array',
                    'items': {
                        'type': 'number'},
                }}],
            'description': 'The training input samples. Internally, it will be converted to'},
        'y': {
            'anyOf': [
                {'type': 'array', 'items': {'type': 'number'}},
                {'type': 'array', 'items': {'type': 'string'}},
                {'type': 'array', 'items': {'type': 'boolean'}}],
            'description': 'The target values (class labels) as integers or strings.'},
        'sample_weight': {
            'anyOf': [{
                'type': 'array',
                'items': {
                    'type': 'number'},
            }, {
                'enum': [None]}],
            'description': 'Sample weights. If None, then samples are equally weighted. Splits'},
        'check_input': {
            'type': 'boolean',
            'default': True,
            'description': 'Allow to bypass several input checking.'},
        'X_idx_sorted': {
            'anyOf': [{
                'type': 'array',
                'items': {
                    'type': 'array',
                    'items': {
                        'type': 'number'},
                }}, {
                'enum': [None]}],
            'default': None,
            'description': 'The indexes of the sorted training input samples. If many tree'},
    },
}
_input_predict_schema = {
    '$schema': 'http://json-schema.org/draft-04/schema#',
    'description': 'Predict class or regression value for X.',
    'type': 'object',
    'properties': {
        'X': {
            'type': 'array',
            'items': {
                'type': 'array',
                'items': {
                    'type': 'number'},
            },
            'description': 'The input samples. Internally, its dtype will be converted to'},
        'check_input': {
            'type': 'boolean',
            'default': True,
            'description': 'Allow to bypass several input checking.'},
    },
}

_output_predict_schema = {
    '$schema': 'http://json-schema.org/draft-04/schema#',
    'description': 'Predicted class label per sample.',
    'anyOf': [
        {'type': 'array', 'items': {'type': 'number'}},
        {'type': 'array', 'items': {'type': 'string'}},
        {'type': 'array', 'items': {'type': 'boolean'}}]}

_input_predict_proba_schema = {
    '$schema': 'http://json-schema.org/draft-04/schema#',
    'description': 'Predict class probabilities of the input samples X.',
    'type': 'object',
    'properties': {
        'X': {
            'anyOf': [{
                'type': 'array',
                'items': {
                    'type': 'array',
                    'items': {
                        'type': 'number'},
                }}],
            'description': 'The input samples. Internally, its dtype will be converted to'},
        'check_input': {
            'type': 'boolean',
            'description': 'Run check_array on X.'},
    },
}

_output_predict_proba_schema = {
    '$schema': 'http://json-schema.org/draft-04/schema#',
    'description': 'Probability of the sample for each class in the model.',
    'type': 'array',
            'items': {
                'type': 'array',
                'items': {
                    'type': 'number'},
            }    
}

_combined_schemas = {
    '$schema': 'http://json-schema.org/draft-04/schema#',
    'description': """`Decision tree classifier`_ from scikit-learn.

.. _`Decision tree classifier`: https://scikit-learn.org/0.20/modules/generated/sklearn.tree.DecisionTreeClassifier.html#sklearn-tree-decisiontreeclassifier
""",
    'documentation_url': 'https://lale.readthedocs.io/en/latest/modules/lale.lib.sklearn.decision_tree_classifier.html',
    'type': 'object',
    'tags': {
        'pre': [],
        'op': ['estimator', 'classifier'],
        'post': []},
    'properties': {
        'hyperparams': _hyperparams_schema,
        'input_fit': _input_fit_schema,
        'input_predict': _input_predict_schema,
        'output_predict': _output_predict_schema,
        'input_predict_proba': _input_predict_proba_schema,
        'output_predict_proba': _output_predict_proba_schema}}


class DecisionTreeClassifierImpl():        

    def __init__(self, criterion='gini', splitter='best', max_depth=None, min_samples_split=2, min_samples_leaf=1, min_weight_fraction_leaf=0.0, max_features=None, random_state=None, max_leaf_nodes=None, min_impurity_decrease=0.0, min_impurity_split=None, class_weight=None, presort=False):
        self._hyperparams = {
            'criterion': criterion,
            'splitter': splitter,
            'max_depth': max_depth,
            'min_samples_split': min_samples_split,
            'min_samples_leaf': min_samples_leaf,
            'min_weight_fraction_leaf': min_weight_fraction_leaf,
            'max_features': max_features,
            'random_state': random_state,
            'max_leaf_nodes': max_leaf_nodes,
            'min_impurity_decrease': min_impurity_decrease,
            'min_impurity_split': min_impurity_split,
            'class_weight': class_weight,
            'presort': presort}
        self._wrapped_model = sklearn.tree.tree.DecisionTreeClassifier(**self._hyperparams)

    def fit(self, X, y, **fit_params):
        if fit_params is None:
            self._wrapped_model.fit(X, y)
        else:
            self._wrapped_model.fit(X, y, **fit_params)
        return self

    def predict(self, X):
        return self._wrapped_model.predict(X)

    def predict_proba(self, X):
        return self._wrapped_model.predict_proba(X)

lale.docstrings.set_docstrings(DecisionTreeClassifierImpl, _combined_schemas)

DecisionTreeClassifier = lale.operators.make_operator(DecisionTreeClassifierImpl, _combined_schemas)