Function computes a diagonal matrix of dimension m+1 by m+1 with i-th entry is the estimated variance of residuals of segment i
psigmq(res, b, q, m, nt)
sigmat (m
+1)x(m
+1) diagonal matrix with i-th entry
equal to estimated variance of regime i
big residual vector of the model
Estimated date of changes
Number of z
regressors
Number of breaks
The size of z
regressors