shrink_into_CH: Identify the position of a point relative to the convex hull...
In ergm: Fit, Simulate and Diagnose Exponential-Family Models for Networks

shrink_into_CH

R Documentation

Identify the position of a point relative to the convex hull of a set of points

Description

This function uses linear programming to find the value by which vector p needs to be scaled towards or away from vector m in order for p to be on the boundary of the convex hull of rows of M. If p is a matrix, a value that scales all rows of p into the convex hull of M is found.

Usage

shrink_into_CH(
  p,
  M,
  m = NULL,
  verbose = FALSE,
  max_run = nrow(M),
  ...,
  solver = c("glpk", "lpsolve")
)

Arguments

`p`	a `d`-dimensional vector or a matrix with `d` columns.
`M`	an `n` by `d` matrix. Each row of `M` is a `d`-dimensional vector.
`m`	a `d`-dimensional vector specifying the value towards which to shrink; must be in the interior of the convex hull of `M`, and defaults to its centroid (column means).
`verbose`	A logical or an integer to control the amount of progress and diagnostic information to be printed. `FALSE`/`0` produces minimal output, with higher values producing more detail. Note that very high values (5+) may significantly slow down processing.
`max_run`	if there are no decreases in step length in this many consecutive test points, conclude that diminishing returns have been reached and finish.
`...`	arguments passed directly to linear program solver.
`solver`	a character string selecting which solver to use; by default, tries `Rglpk`'s but falls back to `lpSolveAPI`'s.

Value

The scaling factor described above is returned. shrink_into_CH() >= 1 indicates that all points in p are in the convex hull of M.

Note

This is a successor to the deprecated function is.inCH(), which was originally written for the "stepping" algorithm of \insertCiteHuHu12i;textualergm. See the updated of \insertCiteKrKu23l;textualergm for detailed discussion of algorithms used in is.inCH() and shrink_into_CH().