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weeknum

(Not recommended; use week) Week in year

weeknum is not recommended. Use the week function instead because it accepts datetime values as inputs. For more information on updating your code, see Version History.

Description

example

N = weeknum(D) returns the week in year. The weeknum function considers the week containing January 1 to be the first week of the year.

example

N = weeknum(___,W,E) returns the week in year using the optional input arguments for W and E. The weeknum function considers the week containing January 1 to be the first week of the year.

Examples

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Determine the week of the year using a serial date number.

N = weeknum(728647)
N = 52

Determine the week of the year using a string.

N = weeknum("19-Dec-1994")
N = 52

Determine the week of the year using a datetime array.

N = weeknum(datetime("19-Dec-1994","Locale","en_US"))
N = 52

The first week of the year must have at least four days in it. For example, January 8, 2004 was a Thursday. The European standard is used because the first week of the year is the first week longer than three days.

weeknum("08-jan-2004",1,1)
ans = 1

You can also use weeknum with datenum.

weeknum(datenum("01-Jan-2004"):datenum("08-Jan-2004"))
ans = 1×8

     1     1     1     2     2     2     2     2

The default start day of the week is Sunday. Every day after, and including the first Sunday of the year (04-Jan-2004), returns 2 denoting the second week. In this case, the first of week of the year started before January 1, 2004. You can also use weeknum with datenum and specify a D value of 5 to indicate that the weeks start on Thursday.

weeknum(datenum("01-Jan-2004"):datenum("08-Jan-2004"),5)
ans = 1×8

     1     1     1     1     1     1     1     2

The first week of the year that has four or more days, based on the specified start day, is considered week one (even if this is not the first week in the calendar). Any day falling in (or before) this week is given a week number of 1.

Input Arguments

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Date to determine week in year, specified as a serial date number, date strings, or datetime array.

Serial date numbers can be a matrix. Date strings can be specified as a string vector or a one-dimensional cell array of character vectors. All the date strings must have the same format.

Use the datestr function to convert serial date numbers to character vectors that are formatted as dates.

Data Types: double | string | char | datetime

Day a week begins, specified as an integer or a vector of integers from 1 through 7.

  • 1 — Sunday (default)

  • 2 — Monday

  • 3 — Tuesday

  • 4 — Wednesday

  • 5 — Thursday

  • 6 — Friday

  • 7 — Saturday

The weeknum function considers the week containing January 1 to be the first week of the year.

Data Types: double

Flag indicates if week of year display is European standard, specified as 1 (to use the European standard) or 0 (not to use the European standard).

The European standard considers first week of year to be first week longer than three days, offset by the given week’s start day.

Data Types: logical

Output Arguments

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Week number of the year, given D, returned as a numeric value, given D, a serial date number, date string, or datetime array. If D is a string vector or a one-dimensional cell array of character vectors, then weeknum returns a column vector of M week numbers, where M is the number of elements in D.

If the optional input arguments W and E are defined, the week of the year is in the European standard.

Version History

Introduced before R2006a

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Not recommended starting in R2022a