findFace {hitandrun}

Find the closest face (constraint) to an interior point of a polytope.

Description

Find the closest face (constraint) to an interior point of a polytope defined by a set of linear constraints.

Usage

findFace(x, constr)

Arguments

x

An interior point

constr

Constraint definition

Details

See har for a description of the constraint definition.

Value

A face index.

Author(s)

Gert van Valkenhoef

See Also

har

Examples

# constraints: x_1 >= 0, x_2 >= 0, x_1 + x_2 <= 1
A <- rbind(c(-1, 0), c(0, -1), c(1, 1))
b <- c(0, 0, 1)
d <- c("<=", "<=", "<=")
constr <- list(constr=A, rhs=b, dir=d)

stopifnot(findFace(c(0.1, 0.2), constr) == 1)
stopifnot(findFace(c(0.2, 0.1), constr) == 2)
stopifnot(findFace(c(0.4, 0.4), constr) == 3)