sklearn.preprocessing
.power_transform¶
-
sklearn.preprocessing.
power_transform
(X, method='box-cox', standardize=True, copy=True)[source]¶ Apply a power transform featurewise to make data more Gaussian-like.
Power transforms are a family of parametric, monotonic transformations that are applied to make data more Gaussian-like. This is useful for modeling issues related to heteroscedasticity (non-constant variance), or other situations where normality is desired.
Currently, power_transform() supports the Box-Cox transform. Box-Cox requires input data to be strictly positive. The optimal parameter for stabilizing variance and minimizing skewness is estimated through maximum likelihood.
By default, zero-mean, unit-variance normalization is applied to the transformed data.
Read more in the User Guide.
Parameters: X : array-like, shape (n_samples, n_features)
The data to be transformed using a power transformation.
method : str, (default=’box-cox’)
The power transform method. Currently, ‘box-cox’ (Box-Cox transform) is the only option available.
standardize : boolean, default=True
Set to True to apply zero-mean, unit-variance normalization to the transformed output.
copy : boolean, optional, default=True
Set to False to perform inplace computation.
See also
PowerTransformer
- Performs power transformation using the
Transformer
API (as part of a preprocessingsklearn.pipeline.Pipeline
). quantile_transform
- Maps data to a standard normal distribution with the parameter output_distribution=’normal’.
Notes
NaNs are treated as missing values: disregarded to compute the statistics, and maintained during the data transformation.
For a comparison of the different scalers, transformers, and normalizers, see examples/preprocessing/plot_all_scaling.py.
References
G.E.P. Box and D.R. Cox, “An Analysis of Transformations”, Journal of the Royal Statistical Society B, 26, 211-252 (1964).
Examples
>>> import numpy as np >>> from sklearn.preprocessing import power_transform >>> data = [[1, 2], [3, 2], [4, 5]] >>> print(power_transform(data)) [[-1.332... -0.707...] [ 0.256... -0.707...] [ 1.076... 1.414...]]