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t c

2005-Oct-11 23:26 UTC

[R] adding 1 month to a date

Within an R dataset, I have a date field called “date_”.  (The dates are in the
format “YYYY-MM-DD”, e.g. “1995-12-01”.)

 

How can I add or subtract “1 month” from this date, to get “1996-01-01” or “
“1995-11-01”.

 


		
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Gabor Grothendieck

2005-Oct-11 23:54 UTC

head link

[R] adding 1 month to a date

Try this:

seq(as.Date("2005-01-15"), len = 2, by = "month")[2]

or here is another approach:

http://finzi.psych.upenn.edu/R/Rhelp02a/archive/61570.html

On 10/11/05, t c <quantpm at yahoo.com> wrote:>
> Within an R dataset, I have a date field called "date_".  (The
dates are in the format "YYYY-MM-DD", e.g. "1995-12-01".)
>
>
>
> How can I add or subtract "1 month" from this date, to get
"1996-01-01" or " "1995-11-01".
>
>
>
>
>
> ---------------------------------
>
>        [[alternative HTML version deleted]]
>
>
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide!
http://www.R-project.org/posting-guide.html
>
>

Marc Schwartz

2005-Oct-12 02:15 UTC

head link

[R] adding 1 month to a date

On Tue, 2005-10-11 at 16:26 -0700, t c wrote:> Within an R dataset, I have a date field called date_.  (The dates are
> in the format YYYY-MM-DD, e.g. 1995-12-01.)
> How can I add or subtract 1 month from this date, to get 1996-01-01 or
> 1995-11-01.
There might be an easier way to do this, but using seq.Date(), you can
increment or decrement from a Time 0 by months:

Add 1 month:

This takes your Time 0, generates a 2 element sequence (which begins
with Time 0) and then takes the second element:
> seq(as.Date("1995-12-01"), by = "month", length = 2)[2][1] "1996-01-01"



Subtract 1 month:

Same as above, but we use 'by = "-1 month"' and take the
second element:
> seq(as.Date("1995-12-01"), by = "-1 month", length =
2)[2][1] "1995-11-01"


See ?as.Date and ?seq.Date for more information. The former function is
used to convert from a character vector to a Date class object. Note
that in your case, the date format is consistent with the default. Pay
attention to the 'format' argument in as.Date() if your dates should be
in other formats.

HTH,

Marc Schwartz

bogdan romocea

2005-Oct-12 12:13 UTC

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[R] adding 1 month to a date

Simple addition and subtraction works as well:
  as.Date("1995/12/01",format="%Y/%m/%d") + 30
If you have datetime values you can use
  strptime("1995-12-01 08:00:00",format="%Y-%m-%d %H:%M:%S")
+ 30*24*3600
where 30*24*3600 = 30 days expressed in seconds.

> -----Original Message-----
> From: Marc Schwartz [mailto:MSchwartz at mn.rr.com]
> Sent: Tuesday, October 11, 2005 10:16 PM
> To: t c
> Cc: r-help at stat.math.ethz.ch
> Subject: Re: [R] adding 1 month to a date
>
>
> On Tue, 2005-10-11 at 16:26 -0700, t c wrote:
> > Within an R dataset, I have a date field called date_.
> (The dates are
> > in the format YYYY-MM-DD, e.g. 1995-12-01.)
>
> > How can I add or subtract 1 month from this date, to get
> 1996-01-01 or
> > 1995-11-01.
>
> There might be an easier way to do this, but using seq.Date(), you can
> increment or decrement from a Time 0 by months:
>
> Add 1 month:
>
> This takes your Time 0, generates a 2 element sequence (which begins
> with Time 0) and then takes the second element:
>
> > seq(as.Date("1995-12-01"), by = "month", length =
2)[2]
> [1] "1996-01-01"
>
>
>
> Subtract 1 month:
>
> Same as above, but we use 'by = "-1 month"' and take the
> second element:
>
> > seq(as.Date("1995-12-01"), by = "-1 month", length
= 2)[2]
> [1] "1995-11-01"
>
>
> See ?as.Date and ?seq.Date for more information. The former
> function is
> used to convert from a character vector to a Date class object. Note
> that in your case, the date format is consistent with the default. Pay
> attention to the 'format' argument in as.Date() if your dates
> should be
> in other formats.
>
> HTH,
>
> Marc Schwartz
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide!
> http://www.R-project.org/posting-guide.html
>

Jim Porzak

2005-Oct-12 16:04 UTC

head link

[R] adding 1 month to a date

OTOH,

 > seq(as.Date("2004-01-31"), by = "month", length = 14)
  [1] "2004-01-31" "2004-03-02" "2004-03-31"
"2004-05-01" "2004-05-31"
  [6] "2004-07-01" "2004-07-31" "2004-08-31"
"2004-10-01" "2004-10-31"
 [11] "2004-12-01" "2004-12-31" "2005-01-31"
"2005-03-03"

 I would prefer to see dates forced to be within each month, not
 "leaking" into next month.

 IOW:
  [1] "2004-01-31" "2004-02-29" "2004-03-31"
"2004-04-30" "2004-05-31", etc


 --
 Jim Porzak
 Loyalty Matrix Inc.
 San Francisco, CA

> On 10/12/05, Marc Schwartz <MSchwartz at mn.rr.com> wrote:
> > Thanks to Prof. Ripley for pointing this out.
> >
> > One of the approaches that I had considered here was to set up a
vector
> > of the number of days in each month (adjusting of course for leap
> > years), and use "day arithmetic" to add/subtract the
appropriate number
> > of days.
> >
> > However, it was easier to use seq.Date() and to further consider
putting
> > a wrapper around it to make it yet even easier to use.
> >
> > Marc
> >
> > On Wed, 2005-10-12 at 13:23 +0100, Prof Brian Ripley wrote:
> > > On Wed, 12 Oct 2005, bogdan romocea wrote:
> > >
> > > > Simple addition and subtraction works as well:
> > > >  as.Date("1995/12/01",format="%Y/%m/%d")
+ 30
> > > > If you have datetime values you can use
> > > >  strptime("1995-12-01
08:00:00",format="%Y-%m-%d %H:%M:%S") + 30*24*3600
> > > > where 30*24*3600 = 30 days expressed in seconds.
> > >
> > > Sorry, not in general, as a month is not generally of 30 days
(including
> > > in your example).
> > >
> > > seq.Date is a good way to do this.
> > >
> > > >
> > > >
> > > >> -----Original Message-----
> > > >> From: Marc Schwartz [mailto:MSchwartz at mn.rr.com]
> > > >> Sent: Tuesday, October 11, 2005 10:16 PM
> > > >> To: t c
> > > >> Cc: r-help at stat.math.ethz.ch
> > > >> Subject: Re: [R] adding 1 month to a date
> > > >>
> > > >>
> > > >> On Tue, 2005-10-11 at 16:26 -0700, t c wrote:
> > > >>> Within an R dataset, I have a date field called
date_.
> > > >> (The dates are
> > > >>> in the format YYYY-MM-DD, e.g. 1995-12-01.)
> > > >>
> > > >>> How can I add or subtract 1 month from this date, to
get
> > > >> 1996-01-01 or
> > > >>> 1995-11-01.
> > > >>
> > > >> There might be an easier way to do this, but using
seq.Date(), you can
> > > >> increment or decrement from a Time 0 by months:
> > > >>
> > > >> Add 1 month:
> > > >>
> > > >> This takes your Time 0, generates a 2 element sequence
(which begins
> > > >> with Time 0) and then takes the second element:
> > > >>
> > > >>> seq(as.Date("1995-12-01"), by =
"month", length = 2)[2]
> > > >> [1] "1996-01-01"
> > > >>
> > > >>
> > > >>
> > > >> Subtract 1 month:
> > > >>
> > > >> Same as above, but we use 'by = "-1
month"' and take the
> > > >> second element:
> > > >>
> > > >>> seq(as.Date("1995-12-01"), by = "-1
month", length = 2)[2]
> > > >> [1] "1995-11-01"
> > > >>
> > > >>
> > > >> See ?as.Date and ?seq.Date for more information. The
former
> > > >> function is
> > > >> used to convert from a character vector to a Date class
object. Note
> > > >> that in your case, the date format is consistent with
the default. Pay
> > > >> attention to the 'format' argument in as.Date()
if your dates
> > > >> should be
> > > >> in other formats.
> > > >>
> > > >> HTH,
> > > >>
> > > >> Marc Schwartz
> >
> > ______________________________________________
> > R-help at stat.math.ethz.ch mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide!
http://www.R-project.org/posting-guide.html
> >
>

David Forrest

2005-Oct-12 16:50 UTC

head link

[R] adding 1 month to a date

On Wed, 12 Oct 2005, Jim Porzak wrote:
>  OTOH,
>
>  > seq(as.Date("2004-01-31"), by = "month", length =
14)
>   [1] "2004-01-31" "2004-03-02" "2004-03-31"
"2004-05-01" "2004-05-31"
>   [6] "2004-07-01" "2004-07-31" "2004-08-31"
"2004-10-01" "2004-10-31"
>  [11] "2004-12-01" "2004-12-31" "2005-01-31"
"2005-03-03"
>
>  I would prefer to see dates forced to be within each month, not
>  "leaking" into next month.
>
>  IOW:
>   [1] "2004-01-31" "2004-02-29" "2004-03-31"
"2004-04-30" "2004-05-31", etc
It depends how you intend "1 month after 2004-01-31".  Is the the same
number of days before the beginning of the next month or after the end of
the stated month?

   seq(as.Date("2004-02-01"), by = "month", length = 14)-1

   [1] "2004-01-31" "2004-02-29" "2004-03-31"
"2004-04-30" "2004-05-31"

Dave
-- 
 Dr. David Forrest
 drf at vims.edu                                    (804)684-7900w
 drf5n at maplepark.com                             (804)642-0662h
                                   http://maplepark.com/~drf5n/

t c

2005-Oct-12 17:52 UTC

head link

[R] adding 1 month to a date

Thanks.  How do I use this to calculate a new variable
(e.g."data$next_month") from an existing variable
(e.g."Data$date_").
 
I tried : <data$next_month<-seq(as.Date(data$date_), len = 2, by =
"month")[2]>,
 
but get the following error message:   "Error in
seq.Date(as.Date(data$date), len = 2, by = "1 month") : 'from'
must be of length 1"
 
Thanks.



Gabor Grothendieck <ggrothendieck@gmail.com> wrote:
Try this:

seq(as.Date("2005-01-15"), len = 2, by = "month")[2]

or here is another approach:

http://finzi.psych.upenn.edu/R/Rhelp02a/archive/61570.html

On 10/11/05, t c wrote:>
> Within an R dataset, I have a date field called "date_". (The
dates are in the format "YYYY-MM-DD", e.g. "1995-12-01".)
>
>
>
> How can I add or subtract "1 month" from this date, to get
"1996-01-01" or " "1995-11-01".
>
>
>
>
>
> ---------------------------------
>
> [[alternative HTML version deleted]]
>
>
>
> ______________________________________________
> R-help@stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide!
http://www.R-project.org/posting-guide.html
>
>

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