fit.1class <- lcmm(fixed = heroin ~ age.std + age2.std + age3.std + female + black + cohort + visit.era,
                   random = ~1,
                   link = "thresholds",
                   subject = "newid",
                   data = alive.complete,
                   verbose = TRUE)

fit <- lcmm(fixed = heroin ~ age.std + age2.std + age3.std + female + black + cohort + visit.era,
            random = ~1,
            mixture = ~ age.std + age2.std + age3.std,
            ng = i,
            link = "thresholds",
            subject = "newid",
            data = alive.complete,
            maxiter = 500,
            B = fit.1class,
            verbose = TRUE)