specials: Formula specials for defining time-dependent covariates
In adibender/ped: What the Package Does (One Line, Title Case)

Description Usage Arguments

So far, two specials are implemented. concurrent is used when the goal is to estimate a concurrent effect of the TDC. cumulative is used when the goal is to estimate a cumulative effect of the TDC. These should usually not be called directly but rather as part of the formula argument to as_ped. See the vignette on data transformation for details.

cumulative(..., tz_var, ll_fun = function(t, tz) t >= tz,
  suffix = NULL)

concurrent(..., tz_var, lag = 0, suffix = NULL)

has_special(formula, special = "cumulative")

`...`	For `concurrent` variables that will be transformed to covariate matrices. The number of columns of each covariate depends on `tz`. Usually, elements that will be specified here are `time` (which should be the name of the time-variable used on the LHS of the formula argument to `as_ped`), `tz` which is the variable containing information on the times at which the TDC was observed (can be wrapped in `latency`) and the TDCs that share the same `tz` and Lag-lead window (`ll_fun`).
`tz_var`	The name of the variable that stores information on the times at which the TDCs specified in this term where observed.
`ll_fun`	Function that specifies how the lag-lead matrix should be constructed. First argument is the follow up time second argument is the time of exposure.
`lag`	a single positive number giving the time lag between for a concurrent effect to occur (i.e., the TDC at time of exposure `t-lag` affects the hazard in the interval containing follow-up time `t`). Defaults to 0.
`formula`	A two sided formula with a `Surv` object on the left-hand-side and covariate specification on the right-hand-side (RHS). The RHS can be an extended formula, which specifies how TDCs should be transformed using specials `concurrent` and `cumulative`.
`special`	The name of the special whose existence in the `formula` should be checked