import numpy as np
from pylops.utils.typing import NDArray
from pyproximal.projection.Box import BoxProj
from pyproximal.ProxOperator import ProxOperator, _check_tau
[docs]
class Box(ProxOperator):
r"""Box proximal operator.
Proximal operator of a Box: :math:`\operatorname{Box}_{[l, u]} = \{ x: l \leq x\leq u \}`.
Parameters
----------
lower : :obj:`float` or :obj:`numpy.ndarray`, optional
Lower bound
upper : :obj:`float` or :obj:`numpy.ndarray`, optional
Upper bound
Notes
-----
As the Box is an indicator function, the proximal operator corresponds to
its orthogonal projection (see :class:`pyproximal.projection.BoxProj` for
details.
"""
def __init__(
self,
lower: float | NDArray = -np.inf,
upper: float | NDArray = np.inf,
) -> None:
super().__init__(None, False)
self.lower = lower
self.upper = upper
self.box = BoxProj(self.lower, self.upper)
def __call__(self, x: NDArray) -> bool:
return bool(np.all((x >= self.lower) & (x <= self.upper)))
@_check_tau
def prox(self, x: NDArray, tau: float) -> NDArray:
return self.box(x)
PyProximal