pl_mrf2d: Pseudo-likelihood function for MRFs on 2d lattices
Description
Computes the pseudo-likelihood function of a Markov Random Field
on a 2-dimensional lattice.
Usage
pl_mrf2d(Z, mrfi, theta, log_scale = TRUE)
Arguments
Z
A matrix with integers in {0,...,C}.
mrfi
A mrfi object representing the
interaction structure.
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.
log_scale
A logical value indicating whether the returned value
should be in logarithmic scale.
Value
A numeric with the pseudo-likelihood value.
Details
The pseudo-likelihood function is defined as the product of
conditional probabilities of each pixel given its neighbors:
$$\prod_i P(Z_i | Z_{{N}_i}, \theta).$$
See Also
A paper with detailed description of the package can be found at
10.18637/jss.v101.i08.