Re: [R] How to get week of the year, scale 1-52?

From: Liaw, Andy <andy_liaw_at_merck.com>
Date: Tue, 18 Mar 2008 09:01:29 -0400

Looks like you can convert to Julian date with the right origin and then divide by 7, and take modulo 52. Something like:

 julian(days, origin=days[1]-1) %/% 7 %% 52

That gets you 0-51. You just need to add one to get what you want. (I subtract one from days[1] because it's a Monday. I'm sure you can figure out how to do that programatically.)

Andy

From: Lauri Nikkinen
>
> R users,
>
> I have a vector of dates
>
> days <- seq(as.Date("2007/1/1"), as.Date("2008/1/31"), "days")
>
> and I would like to have week numbers from 1 to 52 for each year. How
> do I do that? Now I get 00-53 using
>
> format(days, "%W")
>
> > range(format(days, "%W"))
> [1] "00" "53"
>
> I have read "Date and Time Classes in R" (R news 01/04 by Gabor
> Grothendieck and Thomas Petzoldt) with no help.
>
> Thanks
> Lauri
>
> ______________________________________________
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>
>



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