This is a basis function used in simulation algorithms on the Ising
and Potts models. It counts how many of the four neighbours
of $x_{a,b}$ are of the same colour as this
pixel.
Usage
xneig4(x, a, b, col)
Arguments
x
grid of coloured pixels
a
row index
b
column index
col
current or proposed colour
Value
integer between 0 and 4 giving the number of neighbours with the same colour