isoweek function

Calculate the ISO week & year for a Date

This function takes a vector of Date objects and calculates the week and year according to ISO 8601. It is flexible in its output.

isoweek(x, type = "both_num", sep = "-", inv = FALSE,
  colnames = c("isoyear", "isoweek"))

Arguments

• x: A vector of class Date (of length >=1)
• type: A string (one of "week", "year", "both_text", "both_num" or "matrix") that determines the kind of output the function returns. See "Return value".
• sep: Seperator between year and week, applicable if type="both_text"
• inv: If type="both_text", and inv=FALSE, then year comes before week. If inv=TRUE, week comes before year.
• colnames: Names for the matrix columns if type="matrix"

Returns

Different according to the function's type argument. If "both_num" (the default), a vector of 6-digit integers is returned, in a YYYYWW format. If "week" or "year", only the week number or year is returned, respectively. If "both_text", then a character vector of the same length as x is returned, containing both the year and week number, seperated by sep, and inverted if inv=TRUE. Finally, if type="matix", both year and week numbers are returned in a two-column matrix, with the columns named as in colnames.

Details

This function calculates the week number according to ISO 8601. Note that dates near the start or end of a given year may belong to the previous or next year respectively, thus the year needs to be calculated too.

Examples

isoweek(Sys.Date())
isoweek("1980-8-19", "both_text", sep="/", inv=TRUE)
isoweek(c("2004-5-31", "2006-6-10", "2007-8-20"), "matrix")