# Data transformation function for using etm The function transforms a data set in the wide format (i.e., one raw per subject) into the long format (i.e., one raw per transition, and possibly several raws per subjects) in a suitable way for using the `etm` function 1.1 ```r etmprep(time, status, data, tra, state.names, cens.name = NULL, start = NULL, id = NULL, keep) ``` ## Arguments - `time`: A character vector giving the name of the columns containing the transition times or last follow-up times. The length of `time` have to be equal to the number of states, some elements may be NA. See Details. - `status`: A character vector giving the name of the columns indicating whether a state has been visited (0 if not, 1 otherwise). - `data`: A data frame in which to look for the columns specified in `time` and `status`. - `tra`: A quadratic matrix of logical values describing the possible transitions within the multistate model. The $(i, j)$th element of `tra` is TRUE if a transition from state $i$ to state $j$ is possible, FALSE otherwise. The diagonal must be set to FALSE. - `state.names`: A vector of characters giving the states names. If missing, state names are set to be 0:(number of states). - `cens.name`: A character string specifying how censored observations will be indicated in the new data set. Default is NULL, i.e., no censored observation. - `start`: A list containing two elements, `state` and `time`, giving the starting states and times for all individuals. Default is NULL, in which case all individuals are considered to start in the initial state at time 0. - `id`: A character string specifying in which column of `data` the user ids are. Default is NULL, and the ids will be `1:n`. - `keep`: A character vector indicating the column names of the covariate one might want to keep in the new data.frame. ## Details This function only works for irreversible acyclic Markov processes. Therefore, the multistate model will have initial states, into which no transition are possible. For these, NAs are allowed in `time` and `status`. ## Returns The function returns a data.frame suitable for using the `etm` function. The data frame contains the following components: - **id**: Individual id number - **entry**: Entry time into a state - **exit**: Exit time from a state - **from**: State from which a transition occurs - **to**: State into which a transition occurs - **`...`**: Further columns specified in `keep` ## Author(s) Arthur Allignol, arthur.allignol@gmail.com ## See Also `etm` ## Examples ```r ### creation of fake data in the wild format, following an illness-death model ## transition times tdisease <- c(3, 4, 3, 6, 8, 9) tdeath <- c(6, 9, 8, 6, 8, 9) ## transition status stat.disease <- c(1, 1, 1, 0, 0, 0) stat.death <- c(1, 1, 1, 1, 1, 0) ## a covariate that we want to keep in the new data cova <- rbinom(6, 1, 0.5) dat <- data.frame(tdisease, tdeath, stat.disease, stat.death, cova, stringsAsFactors = TRUE) ## Possible transitions tra <- matrix(FALSE, 3, 3) tra[1, 2:3] <- TRUE tra[2, 3] <- TRUE ## data preparation newdat <- etmprep(c(NA, "tdisease", "tdeath"), c(NA, "stat.disease", "stat.death"), data = dat, tra = tra, cens.name = "cens") ```

etmprep function