date_to_cohort_year: Convert dates to one-year cohorts
In johnrbryant/demprep: Prepare Demographic Data

Description Usage Arguments Details Value See Also Examples

Assign dates to one-year cohorts.

1	date_to_cohort_year(date, month_start = "Jan", label_year_start = TRUE)

`date`	Dates of events defining cohorts (typically births). A vector of class `Date`, or a vector that can be coerced to class `Date` via function `as.Date`.
`month_start`	An element of `month.name`, or `month.abb`. Cohorts start on the first day of this month.
`label_year_start`	Logical. Whether to label a cohort by the calendar year at the beginning of the cohort or the calendar year at the end. Defaults to `TRUE`.

Cohorts start on the first day of month_start, and end one-year-minus-one-day later. The default value for month_start is "Jan", so cohorts by default start on 1 January and end on 31 December. month_start can be a full month name or an abbreviation.

If a cohort starts on 1 January, then the first day and last day of the cohort belong to the same calendar year. But if a cohort starts on any other day, then the first day belongs to one calendar year and the last day belongs to the next calendar year. For instance, if a cohort extends from 1 July 2000 to 30 June 2001, then the first day belongs to calendar year 2000, and the last day belongs to calendar year 2001. Some people use the first calendar year to label such cohorts, and others use the last calendar year. For instance, if a cohort extends from 1 July 2000 to 30 June 2001, some people label the cohort "2000", and others label it "2001". Function date_to_cohort_year by default uses the start year. To use the end year, set label_year_start to FALSE.

An integer vector with the same length as date.

The output from date_to_cohort_year is ofen processed further using function format_cohort_year.

Other functions for creating cohorts from dates are date_to_cohort_quarter and and date_to_cohort_month.

Other functions for creating one-year intervals from dates are date_to_age_year, date_to_period_year, and date_to_triangle_year. The interface for date_to_cohort_year is identical to that of date_to_period_year.

date_to_cohort_year(date = c("2024-03-27", "2022-11-09"))

## starts on 1 July rather than 1 January
date_to_cohort_year(date = c("2024-03-27", "2022-11-09"),
                    month_start = "Jul")

## periods starts on 1 July, rather than 1 January, and uses
## calendar year at end, rather than beginning, for the label
date_to_cohort_year(date = c("2024-03-27", "2022-11-09"),
                    month_start = "Jul",
                    label_year_start = FALSE)