def inverse_transform(self, X):
"""
Convert the data back to the original representation.
In case unknown categories are encountered (all zeros in the
one-hot encoding), ``None`` is used to represent this category.
The return type is the same as the type of the input used by the first
call to fit on this estimator instance.
Parameters
----------
X : array-like or sparse matrix, shape [n_samples, n_encoded_features]
The transformed data.
Returns
-------
X_tr : cudf.DataFrame or cupy.ndarray
Inverse transformed array.
"""
self._check_is_fitted()
if cp.sparse.issparse(X):
# cupy.sparse 7.x does not support argmax, when we upgrade cupy to
# 8.x, we should add a condition in the
# if close: `and not cp.sparse.issparsecsc(X)`
# and change the following line by `X = X.tocsc()`
X = X.toarray()
result = DataFrame(columns=self._encoders.keys())
j = 0
for feature in self._encoders.keys():
feature_enc = self._encoders[feature]
cats = feature_enc.classes_
if self.drop is not None:
# Remove dropped categories
dropped_class_idx = Series(self.drop_idx_[feature])
dropped_class_mask = Series(cats).isin(cats[dropped_class_idx])
if len(cats) == 1:
inv = Series(GenericIndex(cats[0]).repeat(X.shape[0]))
result[feature] = inv
continue
cats = cats[~dropped_class_mask]
enc_size = len(cats)
x_feature = X[:, j:j + enc_size]
idx = cp.argmax(x_feature, axis=1)
inv = Series(cats.iloc[idx]).reset_index(drop=True)
if self.handle_unknown == 'ignore':
not_null_idx = x_feature.any(axis=1)
inv.iloc[~not_null_idx] = None
elif self.drop is not None:
# drop will either be None or handle_unknown will be error. If
# self.drop is not None, then we can safely assume that all of
# the nulls in each column are the dropped value
dropped_mask = cp.asarray(x_feature.sum(axis=1) == 0).flatten()
if dropped_mask.any():
inv[dropped_mask] = feature_enc.inverse_transform(
Series(self.drop_idx_[feature]))[0]
result[feature] = inv
j += enc_size
if self.input_type == 'array':
try:
result = cp.asarray(result.as_gpu_matrix())
except ValueError:
warnings.warn("The input one hot encoding contains rows with "
"unknown categories. Arrays do not support null "
"values. Returning output as a DataFrame "
"instead.")
return result
