The unbounded case:
\(\{\theta : a^\top \theta \le b\}\)
(H-representation). The plurality region
\(\{\theta : \theta_1 \le \theta_j\}\) is
normal = e_1 - e_j, offset = 0.
Details
Coordinates are (z, c): z positions a point on the bounding hyperplane
in an orthonormal basis, and c >= 0 is the distance inward.
A halfspace cannot yet be certified; see polytope_region() for the bounded
alternative.
Examples
# `{theta : theta_1 <= theta_2}`
halfspace_region(normal = c(1, -1), offset = 0)
#> <halfspace_region>
#> the halfspace normal . theta <= 0, normal (1, -1), unbounded
#> facets: 1 inequality