Geoffrey:
There may be something for this in one of the packages dealing with dates.
If not, here's one (incomplete) idea, based on something I used for a similar
issue a little while ago. Essentially, make a data frame that ranks each
weekday over a period in ascending order. This data frame could then be merged
in with your data set, with the difference between the "date_num" values for
any two dates equalling the number of weekdays between them.
start.date <- as.Date("2006-01-27")
end.date <- as.Date("2007-08-27")
date.list <- seq(from=start.date, to=end.date, by="day")
date.df <- data.frame(date=date.list, weekday=weekdays(date.list))
date.df <- subset(date.df, subset=!(weekday %in% c("Saturday", "Sunday")))
date.df$date_num <- 1:length(date.df$date)
date.df[1:20,]
> date.df[1:20,]
date weekday date_num
1 2006-01-27 Friday 1
4 2006-01-30 Monday 2
5 2006-01-31 Tuesday 3
6 2006-02-01 Wednesday 4
7 2006-02-02 Thursday 5
8 2006-02-03 Friday 6
11 2006-02-06 Monday 7
12 2006-02-07 Tuesday 8
13 2006-02-08 Wednesday 9
14 2006-02-09 Thursday 10
15 2006-02-10 Friday 11
18 2006-02-13 Monday 12
19 2006-02-14 Tuesday 13
20 2006-02-15 Wednesday 14
21 2006-02-16 Thursday 15
22 2006-02-17 Friday 16
25 2006-02-20 Monday 17
26 2006-02-21 Tuesday 18
27 2006-02-22 Wednesday 19
28 2006-02-23 Thursday 20
-Ian
On May 23, 2011, at 12:30 PM, Geoffrey Smith wrote:
> Thank you for the email. The data is unbalanced, meaning that some days are
> missing. So the sequence of days could be something like Tuesday,
> Wednesday, Friday, Monday. The diff function would produce 1, 2, 3. But I
> would like it to produce 1, 2, 1 since there is really only 1 day between
> Friday and Monday. Thank you. Geoff
>
> On Mon, May 23, 2011 at 10:09 AM, Jeff Newmiller
> <jdnew...@dcn.davis.ca.us>wrote:
>
>> Your request seems bizarre to me. If you really want to ignore the actual
>> time intervals, just do your analysis without the actual dates.
>>
>> If you just want forward-looking time intervals, then put them in the
>> correct index locations.
>>
>> ?diff
>>
>> c(diff(DF$DATE),1)
>> ---------------------------------------------------------------------------
>> Jeff Newmiller The ..... ..... Go Live...
>> DCN:<jdnew...@dcn.davis.ca.us> Basics: ##.#. ##.#. Live Go...
>> Live: OO#.. Dead: OO#.. Playing
>> Research Engineer (Solar/Batteries O.O#. #.O#. with
>> /Software/Embedded Controllers) .OO#. .OO#. rocks...1k
>> ---------------------------------------------------------------------------
>>
>> Sent from my phone. Please excuse my brevity.
>>
>
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>
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