PottsUtils (version 0.2-2)

getWeights: Get All Weights of a Graph

Description

Obtain weights of edges of a 1D, 2D, or 3D graph based on the neighborhood structure.

Usage

getWeights(mask, neiStruc, format=1)

Arguments

mask

a vector, matrix, or 3D array specifying vertices within a graph. Vertices of value 1 are within the graph and 0 are not.

neiStruc

a scalar, vector of four components, or $3\times4$ matrix corresponding to 1D, 2D, or 3D graphs. It specifies the neighborhood structure. See getNeighbors for details.

format

If it is 1, then the output is a vector of weights, one for two vertices in the corresponding output from getEdges. If it is 2, then the output is a matrix, one for two vertices in the corresponding output from getNeighbors.

Value

• A vector of weights, one component corresponding to an edge of a graph. Or a matrix of weights, one component corresponding to two vertices in neighbor.

Details

The weights are equal to the reciprocals of the distance between neighboring vertices.

Examples

#Example 1: get all weights of a 2D graph based on neighborhood structure
  #           corresponding to the first-order Markov random field.
  mask <- matrix(1 ,nrow=2, ncol=3)
  getWeights(mask, neiStruc=c(2,2,0,0))

  #Example 2: get all weights of a 2D graph based on neighborhood structure
  #           corresponding to the second-order Markov random field.
  #           Put the weights in a matrix form corresponding to
  #           neighbors of vertices.
  mask <- matrix(1 ,nrow=3, ncol=3)
  getWeights(mask, neiStruc=c(2,2,2,2), format=2)

  #Example 3: get all weights of a 3D graph based on 6 neighbors structure
  #           where the neighbors of a vertex comprise its available
  #           N,S,E,W, upper and lower adjacencies. 
  mask <- array(1, dim=rep(3,3))
  n61 <- matrix(c(2,2,0,0,
                  0,2,0,0,
                  0,0,0,0), nrow=3, byrow=TRUE)
  getWeights(mask, neiStruc=n61)