diff_flipped_hamiltonian_ising: Diff in Energy of Generalized Ising Model by Single Flip
In XiaoqiLu/ziclust: What the Package Does (One Line, Title Case)

Description Usage Arguments Details Value Examples

diff_flipped_hamilton_ising is a fast-computation method for energy difference, used in the case where only one variable is flipped.

1	diff_flipped_hamiltonian_ising(u, j, h, J = NULL)

`u`	a binary (-1, 1-valued) vector or matrix. If `u` is a matrix, each row is taken as an input vector.
`j`	the (column) index of the variable to be flipped over
`h`	a vector giving the external field.
`J`	a symmetric matrix with zero diagonals giving the interaction. If `J` is `NULL`, the model degenerates to the case of independent binary.

Δ_j E(u \vert h, J) = H(\tilde{u}; h, J) - H(u; h, J),

where \tilde{u}_j = - u_j and \tilde{u}_{-j} = u_{-j}. It can be shown that Δ_j E(u \vert h, J) = 2 u_j (h_j + J_{j, -j} u_{-j}).

a vector giving the energy difference

h <- c(2, 3)
J <- matrix(c(0, -1, -1, 0), 2, 2)
u <- c(-1, +1)
diff_flipped_hamiltonian_ising(u, 2, h, J)

u <- matrix(c(-1, +1, +1, -1), 2, 2, byrow = TRUE)
diff_flipped_hamiltonian_ising(u, 1, h, J)