Simulate multiple trajectories from a multi-state Markov model with arbitrary observation times
Simulate a number of individual realisations from a continuous-time Markov process. Observations of the process are made at specified arbitrary times for each individual, giving panel-observed data.
simmulti.msm(data, qmatrix, covariates=NULL, death = FALSE, start, ematrix=NULL, misccovariates=NULL, hmodel=NULL, hcovariates=NULL, censor.states=NULL, drop.absorb=TRUE)
data |
A data frame with a mandatory column named |
qmatrix |
The transition intensity matrix of the
Markov process, with any covariates set to zero. The diagonal of
|
covariates |
List of linear covariate effects on log transition intensities. Each element is a vector of the effects of one covariate on all the transition intensities. The intensities are ordered by reading across rows of the intensity matrix, starting with the first, counting the positive off-diagonal elements of the matrix. For example, for a multi-state model with three transition
intensities, and two covariates
|
death |
Vector of indices of the death states. A death state is
an absorbing state whose time of entry is known exactly, but the
individual is assumed to be in an unknown transient state ("alive")
at the previous instant. This is the usual situation for times of death in
chronic disease monitoring data. For example, if you specify
|
start |
A vector with the same number of elements as there are distinct subjects in the data, giving the states in which each corresponding individual begins. Or a single number, if all of these are the same. Defaults to state 1 for each subject. |
ematrix |
An optional misclassification matrix for generating observed states
conditionally on the simulated true states. As defined in
|
misccovariates |
Covariate effects on misclassification
probabilities via multinomial logistic regression. Linear effects
operate on the log of each probability relative to the probability of
classification in the correct state. In same format as
|
hmodel |
An optional hidden Markov model for generating observed
outcomes conditionally on the simulated true states. As defined in
|
hcovariates |
List of the same length as
|
censor.states |
Set of simulated states which should be replaced by a censoring indicator at censoring times. By default this is all transient states (representing alive, with unknown state). |
drop.absorb |
Drop repeated observations in the absorbing state, retaining only one. |
sim.msm
is called repeatedly to produce a simulated
trajectory for each individual. The state at each specified
observation time is then taken to produce a new column state
.
The effect of time-dependent covariates on the transition intensity
matrix for an individual is determined by assuming that the covariate is a step function
which remains constant in between the individual's observation times.
If the subject enters an absorbing state, then only the first
observation in that state is kept in the data frame. Rows corresponding to future
observations are deleted. The entry times into states given in
death
are assumed to be known exactly.
A data frame with columns,
subject |
Subject identification indicators |
time |
Observation times |
state |
Simulated (true) state at the corresponding time |
obs |
Observed outcome at the corresponding time, if
|
keep |
Row numbers of the original data. Useful when
|
plus any supplied covariates.
C. H. Jackson chris.jackson@mrc-bsu.cam.ac.uk
### Simulate 100 individuals with common observation times sim.df <- data.frame(subject = rep(1:100, rep(13,100)), time = rep(seq(0, 24, 2), 100)) qmatrix <- rbind(c(-0.11, 0.1, 0.01 ), c(0.05, -0.15, 0.1 ), c(0.02, 0.07, -0.09)) simmulti.msm(sim.df, qmatrix)
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