R help - Feb 2008 - working with weekdays

Dear all, is it possible create, automatically, a variable with all the
Monday and Thursday?

18/02/2008
21/02/2008
25/02/2008
28/02/2008
03/03/2008
.
.
for all months

Best regards

JL
_________________________________________________________________
Confira v?deos com not?cias do NY Times, gols direto do Lance, videocas[[elided
Hotmail spam]]

Try this:

values <- seq(as.Date("2008/01/01"),
as.Date("2008/12/31"), by="days")
values[format(values, "%w") %in% c(1,4)]

On 18/02/2008, lamack lamack <lamac_k at hotmail.com>
wrote:
>
>
> Dear all, is it possible create, automatically, a variable with all the
> Monday and Thursday?
>
> 18/02/2008
> 21/02/2008
> 25/02/2008
> 28/02/2008
> 03/03/2008
> .
> .
> for all months
>
> Best regards
>
> JL
> _________________________________________________________________
> Confira v?deos com not?cias do NY Times, gols direto do Lance,
videocas[[elided Hotmail spam]]
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

-- 
Henrique Dallazuanna
Curitiba-Paran?-Brasil
25? 25' 40" S 49? 16' 22" O

On Mon, 2008-02-18 at 12:56 +0000, lamack lamack wrote:
> 
> Dear all, is it possible create, automatically, a variable with all the
> Monday and Thursday?
> 
> 18/02/2008
> 21/02/2008
> 25/02/2008
> 28/02/2008
> 03/03/2008
> .
> .
> for all months
Here is one way (for all months in 2008), if you know the first
Monday/Thursday
> first.mon <- as.Date("07-01-2008", format =
"%d-%m-%Y")
> first.thu <- as.Date("03-01-2008", format =
"%d-%m-%Y")
> mondays <- seq(from = first.mon, by = "weeks", length = 52)
> thursdays <- seq(from = first.thu, by = "weeks", length = 52)
> sort(c(mondays, thursdays))
  [1] "2008-01-03" "2008-01-07" "2008-01-10"
"2008-01-14" "2008-01-17"
  [6] "2008-01-21".....

And one if you don't:
> days <- seq(as.Date("01-01-2008", format =
"%d-%m-%Y"),
              as.Date("31-12-2008", format = "%d-%m-%Y"), by
= "days") 
> monthu <- days[format(days, format = "%w") %in% c(1,4)]
> all.equal(monthu, sort(c(mondays, thursdays)))
[1] TRUE

HTH

G

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