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weeknum

(Not recommended; use week) Week in year

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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 or Replace Discouraged Instances of Serial Date Numbers and Date Strings.

Syntax

N = weeknum(D)
N = weeknum(___,W,E)

Description

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.

example

Examples

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Open Live Script

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.

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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R2022a: Not recommended

There are no plans to remove weeknum. However, the week function is recommended instead because it accepts datetime values as inputs. The datetime data type provides flexible date and time formats, storage out to nanosecond precision, and properties to account for time zones and daylight saving time.

To return the week in the year, call week with the "weekofyear" argument. If dt is a datetime value, then this week syntax returns the week of the year for dt.

dt = datetime("today")
weekNumber = week(dt,"weekofyear")

See Also

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