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explained_variance.py
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explained_variance.py
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# Copyright The PyTorch Lightning team.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
from typing import Sequence, Tuple, Union
import torch
from torch import Tensor
from torchmetrics.utilities.checks import _check_same_shape
def _explained_variance_update(preds: Tensor, target: Tensor) -> Tuple[int, Tensor, Tensor, Tensor, Tensor]:
"""Updates and returns variables required to compute Explained Variance. Checks for same shape of input
tensors.
Args:
preds: Predicted tensor
target: Ground truth tensor
"""
_check_same_shape(preds, target)
n_obs = preds.size(0)
sum_error = torch.sum(target - preds, dim=0)
diff = target - preds
sum_squared_error = torch.sum(diff * diff, dim=0)
sum_target = torch.sum(target, dim=0)
sum_squared_target = torch.sum(target * target, dim=0)
return n_obs, sum_error, sum_squared_error, sum_target, sum_squared_target
def _explained_variance_compute(
n_obs: Tensor,
sum_error: Tensor,
sum_squared_error: Tensor,
sum_target: Tensor,
sum_squared_target: Tensor,
multioutput: str = "uniform_average",
) -> Tensor:
"""Computes Explained Variance.
Args:
n_obs: Number of predictions or observations
sum_error: Sum of errors over all observations
sum_squared_error: Sum of square of errors over all observations
sum_target: Sum of target values
sum_squared_target: Sum of squares of target values
multioutput: Defines aggregation in the case of multiple output scores. Can be one
of the following strings (default is `'uniform_average'`.):
* `'raw_values'` returns full set of scores
* `'uniform_average'` scores are uniformly averaged
* `'variance_weighted'` scores are weighted by their individual variances
Example:
>>> target = torch.tensor([[0.5, 1], [-1, 1], [7, -6]])
>>> preds = torch.tensor([[0, 2], [-1, 2], [8, -5]])
>>> n_obs, sum_error, ss_error, sum_target, ss_target = _explained_variance_update(preds, target)
>>> _explained_variance_compute(n_obs, sum_error, ss_error, sum_target, ss_target, multioutput='raw_values')
tensor([0.9677, 1.0000])
"""
diff_avg = sum_error / n_obs
numerator = sum_squared_error / n_obs - (diff_avg * diff_avg)
target_avg = sum_target / n_obs
denominator = sum_squared_target / n_obs - (target_avg * target_avg)
# Take care of division by zero
nonzero_numerator = numerator != 0
nonzero_denominator = denominator != 0
valid_score = nonzero_numerator & nonzero_denominator
output_scores = torch.ones_like(diff_avg)
output_scores[valid_score] = 1.0 - (numerator[valid_score] / denominator[valid_score])
output_scores[nonzero_numerator & ~nonzero_denominator] = 0.0
# Decide what to do in multioutput case
# Todo: allow user to pass in tensor with weights
if multioutput == "raw_values":
return output_scores
if multioutput == "uniform_average":
return torch.mean(output_scores)
if multioutput == "variance_weighted":
denom_sum = torch.sum(denominator)
return torch.sum(denominator / denom_sum * output_scores)
def explained_variance(
preds: Tensor,
target: Tensor,
multioutput: str = "uniform_average",
) -> Union[Tensor, Sequence[Tensor]]:
"""Computes explained variance.
Args:
preds: estimated labels
target: ground truth labels
multioutput: Defines aggregation in the case of multiple output scores. Can be one
of the following strings (default is `'uniform_average'`.):
* `'raw_values'` returns full set of scores
* `'uniform_average'` scores are uniformly averaged
* `'variance_weighted'` scores are weighted by their individual variances
Example:
>>> from torchmetrics.functional import explained_variance
>>> target = torch.tensor([3, -0.5, 2, 7])
>>> preds = torch.tensor([2.5, 0.0, 2, 8])
>>> explained_variance(preds, target)
tensor(0.9572)
>>> target = torch.tensor([[0.5, 1], [-1, 1], [7, -6]])
>>> preds = torch.tensor([[0, 2], [-1, 2], [8, -5]])
>>> explained_variance(preds, target, multioutput='raw_values')
tensor([0.9677, 1.0000])
"""
n_obs, sum_error, sum_squared_error, sum_target, sum_squared_target = _explained_variance_update(preds, target)
return _explained_variance_compute(
n_obs,
sum_error,
sum_squared_error,
sum_target,
sum_squared_target,
multioutput,
)