R help - Sep 2016 - get start and end date of ISO weeks giving a date as input

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

### 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"

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


Thanks again for your time, ideas and help!

Best,
Vero


2016-09-08 8:20 GMT-03:00 Luisfo <luisfo89 at 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
>
> ______________________________________________R-help at r-project.org
mailing list -- To UNSUBSCRIBE and more,
seehttps://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
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> and provide commented, minimal, self-contained, reproducible code.
>
>
>
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Hi Veronica,

please see inline.

On Thu, 08 Sep 2016, Veronica Andreo <veroandreo at 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 <luisfo89 at 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

Hello Enrico,

2016-09-08 10:41 GMT-03:00 Enrico Schumann <es at enricoschumann.net>:
> Hi Veronica,
>
> please see inline.
>
> On Thu, 08 Sep 2016, Veronica Andreo <veroandreo at 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
>
Yes! Again, thanks for your time and help!

Best,
Vero

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