Parses Swedish registry dates that may have varying precision (year only, year-month, or full date) and converts them to proper Date objects. Handles common Swedish registry date formats and missing date patterns.
Usage
parse_swedish_date(
date_string,
default_month_day = "0701",
default_day = "15",
na_strings = c("", "NA", "9999", "99999999")
)Arguments
- date_string
Character vector of dates in Swedish registry format
- default_month_day
Character string for default month-day when only year is provided (default: "0701" for July 1st)
- default_day
Character string for default day when only year-month is provided (default: "15" for 15th)
- na_strings
Character vector of strings to treat as NA (default: c("", "NA", "9999", "99999999"))
Details
Swedish registry dates often come in different formats:
4 characters (YYYY): Only year known - adds default_month_day
6 characters (YYYYMM): Year and month known - adds default_day
8 characters (YYYYMMDD): Full date known - uses as-is
Special handling for unknown date components:
"0000" or "9999" endings (unknown month+day) are replaced with default_month_day
"00" or "99" endings (unknown day) are replaced with default_day
Invalid dates return NA with warnings
The "99" convention is used by some quality registries (e.g., Riksstroke) to indicate unknown date components, while "00" is the more common convention.
Examples
# Different date formats
dates <- c("2020", "202003", "20200315", "19990000", "199900", "19990600", "1989-01-01", "")
parse_swedish_date(dates)
#> [1] "2020-07-01" "2020-03-15" "2020-03-15" "1999-07-01" "1999-07-01"
#> [6] "1999-06-15" "1989-01-01" NA
# Custom defaults
parse_swedish_date(dates, default_month_day = "0101", default_day = "01")
#> [1] "2020-01-01" "2020-03-01" "2020-03-15" "1999-01-01" "1999-01-01"
#> [6] "1999-06-01" "1989-01-01" NA