Finds the four TAR columns and creates a new column called tar that pastes the columns into a nice string
Examples
addTarColumn(data.frame(
tarStartWith = 'cohort start',
tarStartOffset = 1,
tarEndWith = 'cohort start',
tarEndOffset = 0
))
#> Found CI TAR columns
#> tarStartWith tarStartOffset tarEndWith tarEndOffset
#> 1 cohort start 1 cohort start 0
#> tar
#> 1 (cohort start + 1) - (cohort start + 0)