sklearn.preprocessing
.RobustScaler¶
- class sklearn.preprocessing.RobustScaler(*, with_centering=True, with_scaling=True, quantile_range=(25.0, 75.0), copy=True, unit_variance=False)[source]¶
Scale features using statistics that are robust to outliers.
This Scaler removes the median and scales the data according to the quantile range (defaults to IQR: Interquartile Range). The IQR is the range between the 1st quartile (25th quantile) and the 3rd quartile (75th quantile).
Centering and scaling happen independently on each feature by computing the relevant statistics on the samples in the training set. Median and interquartile range are then stored to be used on later data using the
transform
method.Standardization of a dataset is a common requirement for many machine learning estimators. Typically this is done by removing the mean and scaling to unit variance. However, outliers can often influence the sample mean / variance in a negative way. In such cases, the median and the interquartile range often give better results.
New in version 0.17.
Read more in the User Guide.
- Parameters
- with_centeringbool, default=True
If True, center the data before scaling. This will cause
transform
to raise an exception when attempted on sparse matrices, because centering them entails building a dense matrix which in common use cases is likely to be too large to fit in memory.- with_scalingbool, default=True
If True, scale the data to interquartile range.
- quantile_rangetuple (q_min, q_max), 0.0 < q_min < q_max < 100.0, default=(25.0, 75.0), == (1st quantile, 3rd quantile), == IQR
Quantile range used to calculate
scale_
.New in version 0.18.
- copybool, default=True
If False, try to avoid a copy and do inplace scaling instead. This is not guaranteed to always work inplace; e.g. if the data is not a NumPy array or scipy.sparse CSR matrix, a copy may still be returned.
- unit_variancebool, default=False
If True, scale data so that normally distributed features have a variance of 1. In general, if the difference between the x-values of
q_max
andq_min
for a standard normal distribution is greater than 1, the dataset will be scaled down. If less than 1, the dataset will be scaled up.New in version 0.24.
- Attributes
- center_array of floats
The median value for each feature in the training set.
- scale_array of floats
The (scaled) interquartile range for each feature in the training set.
New in version 0.17: scale_ attribute.
- n_features_in_int
Number of features seen during fit.
New in version 0.24.
- feature_names_in_ndarray of shape (
n_features_in_
,) Names of features seen during fit. Defined only when
X
has feature names that are all strings.New in version 1.0.
See also
robust_scale
Equivalent function without the estimator API.
PCA
Further removes the linear correlation across features with ‘whiten=True’.
Notes
For a comparison of the different scalers, transformers, and normalizers, see examples/preprocessing/plot_all_scaling.py.
https://en.wikipedia.org/wiki/Median https://en.wikipedia.org/wiki/Interquartile_range
Examples
>>> from sklearn.preprocessing import RobustScaler >>> X = [[ 1., -2., 2.], ... [ -2., 1., 3.], ... [ 4., 1., -2.]] >>> transformer = RobustScaler().fit(X) >>> transformer RobustScaler() >>> transformer.transform(X) array([[ 0. , -2. , 0. ], [-1. , 0. , 0.4], [ 1. , 0. , -1.6]])
Methods
fit
(X[, y])Compute the median and quantiles to be used for scaling.
fit_transform
(X[, y])Fit to data, then transform it.
get_feature_names_out
([input_features])Get output feature names for transformation.
get_params
([deep])Get parameters for this estimator.
Scale back the data to the original representation.
set_params
(**params)Set the parameters of this estimator.
transform
(X)Center and scale the data.
- fit(X, y=None)[source]¶
Compute the median and quantiles to be used for scaling.
- Parameters
- X{array-like, sparse matrix} of shape (n_samples, n_features)
The data used to compute the median and quantiles used for later scaling along the features axis.
- yNone
Ignored.
- Returns
- selfobject
Fitted scaler.
- fit_transform(X, y=None, **fit_params)[source]¶
Fit to data, then transform it.
Fits transformer to
X
andy
with optional parametersfit_params
and returns a transformed version ofX
.- 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_featuresarray-like of str or None, default=None
Input features.
If
input_features
isNone
, thenfeature_names_in_
is used as feature names in. Iffeature_names_in_
is not defined, then names are generated:[x0, x1, ..., x(n_features_in_)]
.If
input_features
is an array-like, theninput_features
must matchfeature_names_in_
iffeature_names_in_
is defined.
- Returns
- feature_names_outndarray of str objects
Same as input features.
- 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.
- inverse_transform(X)[source]¶
Scale back the data to the original representation.
- Parameters
- X{array-like, sparse matrix} of shape (n_samples, n_features)
The rescaled data to be transformed back.
- Returns
- X_tr{ndarray, sparse matrix} of shape (n_samples, n_features)
Transformed array.
- 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.