date2ISOweek {ISOweek}

Converts date from standard notation to week notation according to ISO 8601

Description

This function returns the year, the week of the year, and the day of week of a given date according to ISO 8601. It is an substitute for the %Y-W%V-%u format which is not implemented on Windows.

Usage

  date2ISOweek(date)

Arguments

date

Vector which can be coerced to class Date

Details

According to ISO 8601, the year of the week can differ from the calendar year (see the examples).

Value

A character vector of year, week, and weekday in format "%Y-W%V-%u"

Author(s)

Uwe Block [e-mail]

See Also

strptime for a description of the date formats and references on ISO 8601.

Examples

x <- paste(1999:2011, "-12-31", sep = "")
y <- as.Date(x)
data.frame(date = format(y), weekdate = date2ISOweek(y))
data.frame(date = x, weekdate = date2ISOweek(x))