cr.sparse.opt.indicator_l2_ball¶
- cr.sparse.opt.indicator_l2_ball(q=1.0, b=None, A=None)[source]¶
Returns an indicator function for the closed ball \(\| A x - b \|_2 \leq q\)
- Parameters
q (float) – Radius of the ball
b (jax.numpy.ndarray) – A vector \(b \in \RR^{m}\)
A (jax.numpy.ndarray) – A matrix \(A \in \RR^{m \times n}\)
- Returns
An indicator function
The indicator function is defined as:
(1)¶\[\begin{split}I(x) = \begin{cases} 0 & \text{if } \| A x - b \|_2 \leq q \\ \infty & \text{otherwise} \end{cases}\end{split}\]Special cases:
indicator_l2_ball()
returns the Euclidean unit ball \(\| x \|_2 \leq 1\).indicator_l2_ball(q)
returns the Euclidean ball \(\| x \|_2 \leq q\).indicator_l2_ball(q, b=b)
returns the Euclidean ball at center \(b\), \(\| x - b\|_2 \leq q\).
Notes:
If center \(b \in \RR^m\) is unspecified, we assume the center to be at origin.
If radius \(q\) is unspecified, we assume the radius to be 1.
If the matrix \(A\) is unspecified, we assume \(A\) to be the identity matrix \(I \in \RR^{n \times n}\).