# Copyright 2021 IRT Saint Exupéry, https://www.irt-saintexupery.com
#
# This program is free software; you can redistribute it and/or
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#
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public License
# along with this program; if not, write to the Free Software Foundation,
# Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
#
# Contributors:
#    INITIAL AUTHORS - API and implementation and/or documentation
#        :author: Matthias De Lozzo
#    OTHER AUTHORS   - MACROSCOPIC CHANGES
r"""Standard deviation of the regression model.

Statistics:

.. math::

\sigma[x] = \sqrt{E[(Y(x)-E[Y(x)])^2]}

Bootstrap estimator:

.. math::

\hat{\sigma}[x] = \sqrt{\frac{1}{B-1}\sum_{b=1}^B (Y_b(x)-\widehat{E}[x])^2}

where :math:\widehat{E}[x]= \frac{1}{B}\sum_{b=1}^B Y_b(x).
"""
from __future__ import annotations

from typing import Callable

from numpy.typing import NDArray

[docs]class StandardDeviation(MLDataAcquisitionCriterion):
"""Standard Deviation of the regression model.

This criterion is scaled by the output range.
"""

def _get_func(self) -> Callable[[NDArray[float]], float]:
def func(input_data: NDArray[float]) -> float:
"""Evaluation function.

Args:
input_data: The model input data.

Returns:
The acquisition criterion value.
"""
std = self.algo_distribution.compute_standard_deviation(input_data)
return std / self._scaling_factor

return func