smr_array: Summarized representation of theta arrays

In Freguglia/mrf2d: Markov Random Field Models for Image Analysis

Summarized representation of theta arrays

Description

smr_array creates a vector containing only the free parameters from an array given a restriction family. exapand_array is the reverse operation, expanding a complete array from the vector of sufficient statistics.

Usage

smr_array(theta, family)

expand_array(theta_vec, family, mrfi, C)

Arguments

theta	A 3-dimensional array describing potentials. Slices represent interacting positions, rows represent pixel values and columns represent neighbor values. As an example: theta[1,3,2] has the potential for the pair of values 0,2 observed in the second relative position of mrfi.
family	The family of parameter restrictions to potentials. Families are: 'onepar', 'oneeach', 'absdif', 'dif' or 'free'. See mrf2d-familiy.
theta_vec	A numeric vector with the free parameters of a potential array. It's dimension depends on the restriction family, C and the number of interacting positions on mrfi.
mrfi	A mrfi object representing the interaction structure.
C	The maximum value of the field.

Details

The order the parameters appear in the summarized vector matches the order in smr_stat().

vec_description() provides a data.frame object describing which are the relative positions and interactions associated with each element of the summarized vector in the same order.

Value

smr_array returns a numeric vector with the free parameters of theta.

expand_array returns a three-dimensional array of potentials.

Author(s)

Victor Freguglia

See Also

A paper with detailed description of the package can be found at doi: 10.18637/jss.v101.i08

Examples

smr_array(theta_potts, "onepar")
smr_array(theta_potts, "oneeach")

expand_array(0.99, family = "onepar", mrfi = mrfi(1), C = 2)
expand_array(c(0.1, 0.2), family = "oneeach", mrfi = mrfi(1), C = 3)

Freguglia/mrf2d documentation built on Feb. 13, 2023, 3:29 a.m.