getWeights {PottsUtils}

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. The default value is 1.

Details

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

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.

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)