undersampler

An undersampling transformer to downsample the majority classes in the dataset.

Module Contents

Classes Summary

Undersampler

Initializes an undersampling transformer to downsample the majority classes in the dataset.

Contents

class evalml.pipelines.components.transformers.samplers.undersampler.Undersampler(sampling_ratio=0.25, sampling_ratio_dict=None, min_samples=100, min_percentage=0.1, random_seed=0, **kwargs)[source]

Initializes an undersampling transformer to downsample the majority classes in the dataset.

This component is only run during training and not during predict.

Parameters
  • sampling_ratio (float) – The smallest minority:majority ratio that is accepted as ‘balanced’. For instance, a 1:4 ratio would be represented as 0.25, while a 1:1 ratio is 1.0. Must be between 0 and 1, inclusive. Defaults to 0.25.

  • sampling_ratio_dict (dict) – A dictionary specifying the desired balanced ratio for each target value. For instance, in a binary case where class 1 is the minority, we could specify: sampling_ratio_dict={0: 0.5, 1: 1}, which means we would undersample class 0 to have twice the number of samples as class 1 (minority:majority ratio = 0.5), and don’t sample class 1. Overrides sampling_ratio if provided. Defaults to None.

  • min_samples (int) – The minimum number of samples that we must have for any class, pre or post sampling. If a class must be downsampled, it will not be downsampled past this value. To determine severe imbalance, the minority class must occur less often than this and must have a class ratio below min_percentage. Must be greater than 0. Defaults to 100.

  • min_percentage (float) – The minimum percentage of the minimum class to total dataset that we tolerate, as long as it is above min_samples. If min_percentage and min_samples are not met, treat this as severely imbalanced, and we will not resample the data. Must be between 0 and 0.5, inclusive. Defaults to 0.1.

  • random_seed (int) – The seed to use for random sampling. Defaults to 0.

Raises
  • ValueError – If sampling_ratio is not in the range (0, 1].

  • ValueError – If min_sample is not greater than 0.

  • ValueError – If min_percentage is not between 0 and 0.5, inclusive.

Attributes

hyperparameter_ranges

{}

modifies_features

True

modifies_target

True

name

Undersampler

training_only

True

Methods

clone

Constructs a new component with the same parameters and random state.

default_parameters

Returns the default parameters for this component.

describe

Describe a component and its parameters.

fit

Fits the sampler to the data.

fit_resample

Resampling technique for this sampler.

fit_transform

Fit and transform data using the sampler component.

load

Loads component at file path.

needs_fitting

Returns boolean determining if component needs fitting before calling predict, predict_proba, transform, or feature_importances.

parameters

Returns the parameters which were used to initialize the component.

save

Saves component at file path.

transform

Transforms the input data by sampling the data.

clone(self)

Constructs a new component with the same parameters and random state.

Returns

A new instance of this component with identical parameters and random state.

default_parameters(cls)

Returns the default parameters for this component.

Our convention is that Component.default_parameters == Component().parameters.

Returns

Default parameters for this component.

Return type

dict

describe(self, print_name=False, return_dict=False)

Describe a component and its parameters.

Parameters
  • print_name (bool, optional) – whether to print name of component

  • return_dict (bool, optional) – whether to return description as dictionary in the format {“name”: name, “parameters”: parameters}

Returns

Returns dictionary if return_dict is True, else None.

Return type

None or dict

fit(self, X, y)

Fits the sampler to the data.

Parameters
  • X (pd.DataFrame) – Input features.

  • y (pd.Series) – Target.

Returns

self

Raises

ValueError – If y is None.

fit_resample(self, X, y)[source]

Resampling technique for this sampler.

Parameters
  • X (pd.DataFrame) – Training data to fit and resample.

  • y (pd.Series) – Training data targets to fit and resample.

Returns

Indices to keep for training data.

Return type

list

fit_transform(self, X, y)

Fit and transform data using the sampler component.

Parameters
  • X (pd.DataFrame) – The input training data of shape [n_samples, n_features].

  • y (pd.Series, optional) – The target training data of length [n_samples].

Returns

Transformed data.

Return type

(pd.DataFrame, pd.Series)

static load(file_path)

Loads component at file path.

Parameters

file_path (str) – Location to load file.

Returns

ComponentBase object

needs_fitting(self)

Returns boolean determining if component needs fitting before calling predict, predict_proba, transform, or feature_importances.

This can be overridden to False for components that do not need to be fit or whose fit methods do nothing.

Returns

True.

property parameters(self)

Returns the parameters which were used to initialize the component.

save(self, file_path, pickle_protocol=cloudpickle.DEFAULT_PROTOCOL)

Saves component at file path.

Parameters
  • file_path (str) – Location to save file.

  • pickle_protocol (int) – The pickle data stream format.

transform(self, X, y=None)[source]

Transforms the input data by sampling the data.

Parameters
  • X (pd.DataFrame) – Training features.

  • y (pd.Series) – Target.

Returns

Transformed features and target.

Return type

pd.DataFrame, pd.Series