tdc_stat: stats for tdc
In renlund/dm: Data Management

Attempt to describe a time dependent covariate (tdc). survival::tmerge creates time periods (per patient) starting at 'tstart' and ending at 'tstop'. This function calculates a statistic at each time point of interest (set of all distinct time points starting or ending an interval). For each such point, the values of a tdc is gathered to calculate a statistic (determined by argument 'stat').

1	tdc_stat(x, var, stat, stat.names = NULL, tstart = "tstart", tstop = "tstop")

`x`	data frame with time periods starting at tstart, ending at tstop.
`var`	name of variable of interest
`stat`	function to calculate stat. Note: can return a vector
`stat.names`	names of columns created, if set to NULL, the function will provide them
`tstart`	name of variable acting as tstart
`tstop`	name of variable acting as tstop