Hi Veronica,
please see inline.
On Thu, 08 Sep 2016, Veronica Andreo <veroand...@gmail.com> writes:
> Hello Luisfo and Enrico,
>
> Thanks for your help! I've been testing both
> solutions... results differ for the same date (I
> changed both functions to use ISO8601). And I added
> contiguous dates, to see how they handle the
> start-end of the week.
>
> So, here the results:
>
> ### one example
> d <- c("2010-08-21","2010-08-22","2010-08-23","2010-08-24")
> iso_start_end <- function(d) {
> d <- as.Date(d)
> wday <- as.POSIXlt(d)$wday
> data.frame(date = d,
> week = format(d, "%V"),
> starts = d - wday + 1,
> ends = d + 7 - wday)
> }
> iso_start_end(d)
>
> date week starts ends
> 1 2010-08-21 33 2010-08-16 2010-08-22
> 2 2010-08-22 33 2010-08-23 2010-08-29
> 3 2010-08-23 34 2010-08-23 2010-08-29
> 4 2010-08-24 34 2010-08-23 2010-08-29
Yes, the second date makes no sense, and it happens
because Sunday is 0 (and not 7). My bad. Here is
a fixed version:
iso_start_end <- function(d) {
d <- as.Date(d)
wday <- as.POSIXlt(d)$wday
wday[wday == 0] <- 7
data.frame(date = d,
week = format(d, "%V"),
starts = d - wday + 1,
ends = d + 7 - wday)
}
> ### the other example:
> dd <- as.Date(strptime('2010-08-21', format="%Y-%m-%d", tz="GMT"))
> ref.date <- as.Date(strptime(paste0(year(dd),"-01-01"), format="%Y-%m-%d"))
> bound.dates <- ref.date + 7 * (isoweek(dd)) + c(0,6)
> bound.dates
> [1] "2010-08-20" "2010-08-26"
You can use the function "weekdays" to see check the
results.
> weekdays(bound.dates)
[1] "Friday" "Thursday"
> So, researching a bit more and inspired by those
> examples, I eventually came up with this solution
> that seems to work fine... I share in case that any
> other has a similar problem:
>
> # get ISOweek for my vector of dates
> week_iso<-ISOweek(d)
>
> # vector with the format %Y-W%V-1 for start day of the ISO week
> week_iso_day1 <- paste(week_iso,1, sep="-")
>
> # vector with the format %Y-W%V-7 for end day of the ISO week
> week_iso_day7 <- paste(week_iso, 7, sep="-")
>
> # use ISOweek2date
> data.frame(date= d, week_iso = week_iso, start = ISOweek2date(week_iso_day1),
> end = ISOweek2date(week_iso_day7)
>
> date week_iso start end
> 1 2010-08-21 2010-W33 2010-08-16 2010-08-22
> 2 2010-08-22 2010-W33 2010-08-16 2010-08-22
> 3 2010-08-23 2010-W34 2010-08-23 2010-08-29
> 4 2010-08-24 2010-W34 2010-08-23 2010-08-29
The updated 'iso_start_end' gives the same result.
date week starts ends
1 2010-08-21 33 2010-08-16 2010-08-22
2 2010-08-22 33 2010-08-16 2010-08-22
3 2010-08-23 34 2010-08-23 2010-08-29
4 2010-08-24 34 2010-08-23 2010-08-29
Kind regards
Enrico
> Thanks again for your time, ideas and help!
>
> Best,
> Vero
>
> 2016-09-08 8:20 GMT-03:00 Luisfo <luisf...@yahoo.es>:
>
> Dear Veronica,
>
> Here there's a way of doing what you requested.
>
> library("lubridate")
> # your date '2010-08-21' as Date object
> dd <- as.Date(strptime("2010-08-21", format="%Y-%m-%d", tz="GMT"))
> # take the first day of the year as Date object, i.e. 2010-01-01 in our
> example
> ref.date <- as.Date(strptime(paste0(year(dd),"-01-01"),
> format="%Y-%m-%d", tz="GMT"))
> # the start and end dates
> bound.dates <- ref.date + 7 * (week(dd)-1) + c(0,6)
>
> I hope you find it useful.
>
> Best,
>
> Luisfo Chiroque
> PhD Student | PhD Candidate
> IMDEA Networks Institute
> http://fourier.networks.imdea.org/people/~luis_nunez/
>
> On 09/08/2016 12:13 PM, Veronica Andreo wrote:
>
> Hello list,
>
> Is there a quick way to get start and end date (%Y-%m-%d) from ISO
> weeks if I only have dates?
>
> For example, I have this date in which some event happened:
> "2010-08-21". Not only I want the ISO week, which I can obtain either
> with isoweek (lubridate) or ISOweek (ISOweek), but I want the start
> and end date of that ISO week.
>
> Do I need to print all ISO weeks from the period of interest and
> sample there for start and end date? Or is there a better way to do
> that?
>
> Thanks a lot in advance!
>
> Best,
> Veronica
>
--
Enrico Schumann
Lucerne, Switzerland
http://enricoschumann.net
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