Simulate health state transitions in a cohort discrete time state transition model.

## Format

An R6::R6Class object.

create_CohortDtstmTrans() creates a CohortDtstmTrans object from either a fitted statistical model or a parameter object. A complete economic model can be implemented with the CohortDtstm class.

## Public fields

params

Parameters for simulating health state transitions. Supports objects of class tparams_transprobs or params_mlogit_list.

input_data

An object of class input_mats.

cycle_length

The length of a model cycle in terms of years. The default is 1 meaning that model cycles are 1 year long.

absorbing

A numeric vector denoting the states that are absorbing states; i.e., states that cannot be transitioned from. Each element should correspond to a state_id, which should, in turn, be the index of the health state.

## Active bindings

start_stateprobs

A non-negative vector with length equal to the number of health states containing the probability that the cohort is in each health state at the start of the simulation. For example, if there were three states and the cohort began the simulation in state 1, then start_stateprobs = c(1, 0, 0). Automatically normalized to sum to 1. If NULL, then a vector with the first element equal to 1 and all remaining elements equal to 0.

trans_mat

A transition matrix describing the states and transitions in a discrete-time multi-state model. Only required if the model is parameterized using multinomial logistic regression. The (i,j) element represents a transition from state i to state j. Each possible transition from row i should be based on a separate multinomial logistic regression and ordered from 0 to K - 1 where K is the number of possible transitions. Transitions that are not possible should be NA. and the reference category for each row should be 0.

## Methods

### Method new()

Create a new CohortDtstmTrans object.

#### Arguments

n_cycles

The number of model cycles to simulate the model for.

#### Returns

An object of class stateprobs.

### Method clone()

The objects of this class are cloneable with this method.

CohortDtstmTrans$clone(deep = FALSE) #### Arguments deep Whether to make a deep clone. ## Examples library("msm") library("data.table") set.seed(101) # We consider two examples that have the same treatment strategies and patients. # One model is parameterized by fitting a multi-state model with the "msm" # package; in the second model, the parameters are entered "manually" with # a "params_mlogit_list" object. # MODEL SETUP strategies <- data.table( strategy_id = c(1, 2, 3), strategy_name = c("SOC", "New 1", "New 2") ) patients <- data.table(patient_id = 1:2) hesim_dat <- hesim_data( strategies = strategies, patients = patients ) # EXAMPLE #1: msm ## Fit multi-state model with panel data via msm qinit <- rbind( c(0, 0.28163, 0.01239), c(0, 0, 0.10204), c(0, 0, 0) ) fit <- msm(state_id ~ time, subject = patient_id, data = onc3p[patient_id %in% sample(patient_id, 100)], covariates = list("1-2" =~ strategy_name), qmatrix = qinit) ## Simulation model transmod_data <- expand(hesim_dat) transmod <- create_CohortDtstmTrans(fit, input_data = transmod_data, cycle_length = 1/2, fixedpars = 2, n = 2) transmod$sim_stateprobs(n_cycles = 2)
#>      sample strategy_id patient_id grp_id state_id   t        prob
#>   1:      1           1          1      1        1 0.0 1.000000000
#>   2:      1           1          1      1        1 0.5 0.792695102
#>   3:      1           1          1      1        1 1.0 0.628365524
#>   4:      1           1          1      1        2 0.0 0.000000000
#>   5:      1           1          1      1        2 0.5 0.202046511
#>  ---
#> 104:      2           3          2      1        2 0.5 0.184425447
#> 105:      2           3          2      1        2 1.0 0.325475890
#> 106:      2           3          2      1        3 0.0 0.000000000
#> 107:      2           3          2      1        3 0.5 0.004553194
#> 108:      2           3          2      1        3 1.0 0.016768466
# EXAMPLE #2: params_mlogit_list
## Input data
transmod_data[, intercept := 1]
#>    strategy_id patient_id strategy_name intercept
#> 1:           1          1           SOC         1
#> 2:           1          2           SOC         1
#> 3:           2          1         New 1         1
#> 4:           2          2         New 1         1
#> 5:           3          1         New 2         1
#> 6:           3          2         New 2         1transmod_data[, new1 := ifelse(strategy_name == "New 1", 1, 0)]
#>    strategy_id patient_id strategy_name intercept new1
#> 1:           1          1           SOC         1    0
#> 2:           1          2           SOC         1    0
#> 3:           2          1         New 1         1    1
#> 4:           2          2         New 1         1    1
#> 5:           3          1         New 2         1    0
#> 6:           3          2         New 2         1    0transmod_data[, new2 := ifelse(strategy_name == "New 2", 1, 0)]
#>    strategy_id patient_id strategy_name intercept new1 new2
#> 1:           1          1           SOC         1    0    0
#> 2:           1          2           SOC         1    0    0
#> 3:           2          1         New 1         1    1    0
#> 4:           2          2         New 1         1    1    0
#> 5:           3          1         New 2         1    0    1
#> 6:           3          2         New 2         1    0    1
## Parameters
n <- 10
transmod_params <- params_mlogit_list(

## Transitions from stable state (stable -> progression, stable -> death)
stable = params_mlogit(
coefs = list(
progression = data.frame(
intercept = rnorm(n, -0.65, .1),
new1 = rnorm(n, log(.8), .02),
new2 = rnorm(n, log(.7, .02))
),
death = data.frame(
intercept = rnorm(n, -3.75, .1),
new1 = rep(0, n),
new2 = rep(0, n)
)
)
),

## Transition from progression state (progression -> death)
progression = params_mlogit(
coefs = list(
death = data.frame(
intercept = rnorm(n, 2.45, .1),
new1 = rep(0, n),
new2 = rep(0, n)
)
)
)
)
transmod_params
#> A "params_mlogit_list" object
#>
#> Summary of coefficients:
#>           from          to      term       mean         sd       2.5%
#> 1:      stable progression intercept -0.6634794 0.05869755 -0.7388932
#> 2:      stable progression      new1 -0.2152838 0.01251555 -0.2372537
#> 3:      stable progression      new2 -0.2360914 1.24487406 -2.0402193
#> 4:      stable       death intercept -3.7448951 0.09512508 -3.8635279
#> 5:      stable       death      new1  0.0000000 0.00000000  0.0000000
#> 6:      stable       death      new2  0.0000000 0.00000000  0.0000000
#> 7: progression       death intercept  2.4654098 0.07608317  2.3275534
#> 8: progression       death      new1  0.0000000 0.00000000  0.0000000
#> 9: progression       death      new2  0.0000000 0.00000000  0.0000000
#>         97.5%
#> 1: -0.5587877
#> 2: -0.1993740
#> 3:  1.9666138
#> 4: -3.6104667
#> 5:  0.0000000
#> 6:  0.0000000
#> 7:  2.5418337
#> 8:  0.0000000
#> 9:  0.0000000
#>
#> Number of parameter samples: 10
#> Number of starting (non-absorbing) states: 2
#> Number of transitions by starting state: 2 1
## Simulation model
tmat <- rbind(c(0, 1, 2),
c(NA, 0, 1),
c(NA, NA, NA))
transmod <- create_CohortDtstmTrans(transmod_params,
input_data = transmod_data,
trans_mat = tmat, cycle_length = 1)
transmod$sim_stateprobs(n_cycles = 2) #> sample strategy_id patient_id grp_id state_id t prob #> 1: 1 1 1 1 1 0 1.000000000 #> 2: 1 1 1 1 1 1 0.644542208 #> 3: 1 1 1 1 1 2 0.415434658 #> 4: 1 1 1 1 2 0 0.000000000 #> 5: 1 1 1 1 2 1 0.338329178 #> --- #> 536: 10 3 2 1 2 1 0.842673723 #> 537: 10 3 2 1 2 2 0.191956639 #> 538: 10 3 2 1 3 0 0.000000000 #> 539: 10 3 2 1 3 1 0.003998375 #> 540: 10 3 2 1 3 2 0.784533916 # \dontshow{ pb <- expmat(coef(fit)$baseline)[, , 1]

## From stable
b1 <- log(pb[1, 2]/(1 - pb[1, 2] - pb[1, 3]))
b2 <- log(pb[1, 3]/(1 - pb[1, 2] - pb[1, 3]))
exp(b1)/(1 + exp(b1) + exp(b2))
#> [1] 0.3379348  exp(b2)/(1 + exp(b1) + exp(b2))
#> [1] 0.01522282
### From progression
b <- qlogis(pb[2, 2])
# }