visit_sum function

Create Visit Sum Covariate

This internal function assists in the implementation of a visit process by creating a covariate, ts_visit, that counts the number of visits in the past max_visits time points. If this number is greater than 0, then the individual has not missed more than the maximum number of visits.

visit_sum(pool, histvars, time_name, t, id_name, max_visits)

Arguments

• pool: Data table containing all information prior to time $t$ ($t$ noninclusive).
• histvars: Vector of character strings specifying the names of the variables for which lagged cumulative averages are to be created.
• time_name: Character string specifying the name of the time variable in pool.
• t: Integer specifying the current time index.
• id_name: Character string specifying the name of the ID variable in pool.
• max_visits: A vector of one or more values denoting the maximum number of times a binary covariate representing a visit process may be missed before the individual is censored from the data (in the observed data) or a visit is forced (in the simulated data). Multiple values exist in the vector when the modeling of more than covariate is attached to a visit process.

Returns

No value is returned. The data table pool is modified in place.