WBS.network {changepoints} | R Documentation |
Perform wild binary segmentation for network change points detection.
WBS.network(data_mat1, data_mat2, s, e, Alpha, Beta, delta, level = 0)
data_mat1 |
A |
data_mat2 |
An independent copy of data_mat1. |
s |
A |
e |
A |
Alpha |
A |
Beta |
A |
delta |
A positive |
level |
Should be fixed as 0. |
An object of class
"BS", which is a list
with the following structure:
S |
A vector of estimated change points (sorted in strictly increasing order). |
Dval |
A vector of values of CUSUM statistic based on KS distance. |
Level |
A vector representing the levels at which each change point is detected. |
Parent |
A matrix with the starting indices on the first row and the ending indices on the second row. |
Daren Wang & Haotian Xu
Wang, Yu and Rinaldo (2018) <arxiv:1809.09602>.
thresholdBS
for obtaining change points estimation.
p = 15 # number of nodes
rho = 0.5 # sparsity parameter
block_num = 3 # number of groups for SBM
n = 100 # sample size for each segment
# connectivity matrix for the first and the third segments
conn1_mat = rho * matrix(c(0.6,1,0.6,1,0.6,0.5,0.6,0.5,0.6), nrow = 3)
# connectivity matrix for the second segment
conn2_mat = rho * matrix(c(0.6,0.5,0.6,0.5,0.6,1,0.6,1,0.6), nrow = 3)
set.seed(1)
can_vec = sample(1:p, replace = FALSE) # randomly assign nodes into groups
sbm1 = simu.SBM(conn1_mat, can_vec, n, symm = TRUE, self = TRUE)
sbm2 = simu.SBM(conn2_mat, can_vec, n, symm = TRUE, self = TRUE)
data_mat = cbind(sbm1$obs_mat, sbm2$obs_mat)
data_mat1 = data_mat[,seq(1,ncol(data_mat),2)]
data_mat2 = data_mat[,seq(2,ncol(data_mat),2)]
M = 10
intervals = WBS.intervals(M = M, lower = 1, upper = ncol(data_mat1))
temp = WBS.network(data_mat1, data_mat2, 1, ncol(data_mat1),
intervals$Alpha, intervals$Beta, delta = 5)
rho_hat = quantile(rowMeans(data_mat), 0.95)
tau = p*rho_hat*(log(n))^2/20 # default threshold given in the paper
cpt_init = unlist(thresholdBS(temp, tau)$cpt_hat[,1])
cpt_refined = local.refine.network(cpt_init, data_mat1, data_mat2,
self = TRUE, tau2 = p*rho_hat/3, tau3 = Inf)
cpt_WBS = 2*cpt_init
cpt_refined = 2*cpt_refined