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 preprocessing 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, using the median and the interquartile range often give better results. For an example visualization and comparison to other scalers, refer to Compare RobustScaler with other scalers.
Added in version 0.17.
Read more in the User Guide.
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.
If True
, scale the data to interquartile range.
Quantile range used to calculate scale_
. By default this is equal to the IQR, i.e., q_min
is the first quantile and q_max
is the third quantile.
Added in version 0.18.
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.
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
and q_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.
Added in version 0.24.
The median value for each feature in the training set.
The (scaled) interquartile range for each feature in the training set.
Added in version 0.17: scale_ attribute.
Number of features seen during fit.
Added in version 0.24.
n_features_in_
,)
Names of features seen during fit. Defined only when X
has feature names that are all strings.
Added in version 1.0.
Notes
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]])
Compute the median and quantiles to be used for scaling.
The data used to compute the median and quantiles used for later scaling along the features axis.
Not used, present here for API consistency by convention.
Fitted scaler.
Fit to data, then transform it.
Fits transformer to X
and y
with optional parameters fit_params
and returns a transformed version of X
.
Input samples.
Target values (None for unsupervised transformations).
Additional fit parameters.
Transformed array.
Get output feature names for transformation.
Input features.
If input_features
is None
, then feature_names_in_
is used as feature names in. If feature_names_in_
is not defined, then the following input feature names are generated: ["x0", "x1", ..., "x(n_features_in_ - 1)"]
.
If input_features
is an array-like, then input_features
must match feature_names_in_
if feature_names_in_
is defined.
Same as input features.
Get metadata routing of this object.
Please check User Guide on how the routing mechanism works.
A MetadataRequest
encapsulating routing information.
Get parameters for this estimator.
If True, will return the parameters for this estimator and contained subobjects that are estimators.
Parameter names mapped to their values.
Scale back the data to the original representation.
The rescaled data to be transformed back.
Transformed array.
Set output container.
See Introducing the set_output API for an example on how to use the API.
Configure output of transform
and fit_transform
.
"default"
: Default output format of a transformer
"pandas"
: DataFrame output
"polars"
: Polars output
None
: Transform configuration is unchanged
Added in version 1.4: "polars"
option was added.
Estimator instance.
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.
Estimator parameters.
Estimator instance.
Center and scale the data.
The data used to scale along the specified axis.
Transformed array.
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