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Subject: Re: [office-formula] WEEKNUM reference
Hi David, On Thursday, 2007-02-22 10:56:03 -0500, David A. Wheeler wrote: > Wheeler: > > > 1. Simple/absolute weeks > > > We can cover the "absolute/simple" week number system with a trivial modification to WEEKNUM. Here's a proposal: if WEEKNUM's second parameter is "0", then the simple week number is returned. That would mean that WEEKNUM(d;0) == WEEKNUM(x; WEEKDAY(DATE(1;1;YEAR(x))). > > Eike: > > Apart from that it would be DATE(YEAR(x);1;1) instead, I don't see why > > WEEKNUM(d;0) would be equal to WEEKNUM(x;n) with n!=0. > > Ooops, I changed the unbound variable midways through. Bad me! Let me try again; what I meant was: > WEEKNUM(x;0) == WEEKNUM(x; WEEKDAY(DATE(1;1;YEAR(x))) I still don't see how that's meant. Maybe a misunderstanding from mixing absolute and simple weeks. From my understanding the definitions are: 1. Absolute week, as used by US military: The first 7 days of a year are the first week, regardless of the day-of-week the year started with, days 8-14 are the second week, and so on. This would be covered with a 2nd argument of 0. 2. Simple weeks, as used in many countries not following ISO 8601 and implemented by Excel: Week 1 always is the week containing January 1, week number changes to week 2 as soon as the start-day-of-week is reached. Remaining days of the first week in the previous year are always in week 53 respectively 54 of that year. > Eike: > > Actually quite a few locales not using ISO 8601 week numbering use > > minimum-number-of-days 1, resulting in the first week of the year being > > the week where the first start-of-week-day of that year is, which would > > be covered by your 1..7 proposal above. > > > > Some, similar to ISO 8601, use minimum-number-of-days 4, but with Sunday > > as start-of-week-day. These would need extra handling. Currently the > > locales are *-CA Canada and *-MT Malta, according to the CLDR > > supplementalData.xml > > Eek. Okay, I stand corrected. > > Okay, I think there's wide agreement that we need to _AT LEAST_ add support for 1..7 as the second parameter. > > Should we add the optional 3rd parameter for "minimum number of days in a week?? Yes, we should, so we can support > "0" for simple years? No, 1; see definition of simple week #2 and my previous explanation above. For absolute weeks (argument2 = 0) the parameter is meaningless and must be ignored. Eike -- Automatic string conversions considered dangerous. They are the GOTO statements of spreadsheets. --Robert Weir on the OpenDocument formula subcommittee's list.
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