ExclusionTransformer.py

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from ._CustomTransformer import _CustomTransformer
 
import numpy as np 
 
 
class ExclusionTransformer(_CustomTransformer):
    ''' 
    Exclude certain columns from being transformed by the given transformer.
    The passed in transformer should be a transformer class, and exclude_slice can
    be any object which, when used to slice a numpy array, will give the 
    appropriate columns which should be excluded. So, for example:
        - slice(1)
        - slice(-3, None)
        - slice(1,None,2)
        - np.array([True, False, False, True])
        etc.
    '''
    def __init__(self, exclude_slice, transformer, transformer_args=[], transformer_kwargs={}):
        self.transformer = transformer(*transformer_args, **transformer_kwargs)
        self.excl = exclude_slice
 
    def _fit(self, X, *args, **kwargs):
        cols = np.arange(X.shape[1])
        cols = [c for c in cols if c not in cols[self.excl]]
        self.transformer.fit(X[:, cols])
        self.keep = cols
 
    def _transform(self, X, *args, **kwargs):
        Z = np.zeros_like(X)
        Z[:, self.keep] = self.transformer.transform(X[:, self.keep])
        Z[:, self.excl] = X[:, self.excl]
        return Z 
 
    def _inverse_transform(self, X, *args, **kwargs):
        Z = np.zeros_like(X)
        Z[:, self.keep] = self.transformer.inverse_transform(X[:, self.keep])
        Z[:, self.excl] = X[:, self.excl]
        return Z