Call:
ddhazard(formula = survival::Surv(stop, event) ~ group, data = head_neck_cancer, 
    by = 1, max_T = 20, a_0 = rep(0, 2), Q_0 = diag(1, 2), Q = diag(0.1, 
        2), order = 1, control = list(eps = 0.1))

'logit' model fitted with the 'EKF' method in 2 iterations of the EM algorithm.

Smoothed time-varying coefficients are:
   (Intercept)       sd 
 0   -2.806424 0.4064023
 2   -2.882709 0.3038966
 4   -2.493780 0.3060795
 6   -2.220863 0.2842865
 9   -2.888184 0.3244203
11   -3.211450 0.3551100
13   -3.398163 0.3907957
16   -3.455511 0.4285787
18   -3.479997 0.4831253
20   -3.421549 0.5820568

The estimated diagonal entries of the covariance matrix in the state equation are:
(Intercept)      group1 
 0.10291497  0.09050972 

96 individuals used in estimation with 65 observed events.
