I'm assuming that by day_number is the day of the year rather than "day number"
as defined in the dates script.
Here's a go at the simple one:
yearmonth=: [: 2&[EMAIL PROTECTED] todayno@(,&1 1)@{. + <:@{:
yearmonth 2008 31
2008 1
yearmonth 2008 32
2008 2
yearmonth 2008 60
2008 2
yearmonth 2009 60
2009 3
>From http://en.wikipedia.org/wiki/Week#Week_number it seems there are a number
>of different ways of determining week number.
The following prototype of a yearweek verb follows the ISO rules. I imagine the
logic could be simplified a bit though!!
yearweek=: 3 : 0
'yr daynum'=. y
b=. 7| _1+yr+-/<.4 100 400%~<:yr
md=. 28+3,(~:/0=4 100 400|yr),10$5$3 2
wks=. _7]\(-b)|. (7*53) {. >:i.+/md
wk=. I. daynum e."1 ] wks
if. (wk=52)*. 3 > 0 i:&1@:< {:wks do.
wk=. 1
yr=. >:yr
else.
if. b>3 do. NB. adjust for first week
if. wk = 0 do.
'yr wk'=. yearweek (<:yr),365
end.
else. NB.
wk=. >:wk
end.
end.
yr,wk
)
yearweek 2010 1
2009 53
yearweek 2010 8
2010 1
yearweek 2006 365
2006 52
yearweek 2006 1
2005 52
---david alis wrote:
> I need two conversion verbs:
> (year,day_number) into (year,week_number)
> for example - (2010,1) -> (2009,53)
> (1.Jan.2010 is in Week 53 of 2009)
>
> and the simpler:
> (year, day_number) into (year, month_number)
----------------------------------------------------------------------
For information about J forums see http://www.jsoftware.com/forums.htm
