[LONGITUDINAL]
input = {a, b, c, d}

EQUATION:
l12 = a+b*t
l21 = c+d*t
p12 = 1/(1+exp(-l12))
p21 = 1/(1+exp(-l21))

DEFINITION:
y = {type       = categorical
     categories = {1, 2}
     dependence = Markov
     logit(P(y=2 |y_p=1))=l12
     logit(P(y=1 |y_p=2))=l21}