[R] Convert number to Date

[Nordlund, Dan (DSHS/RDA)]

Rolf,

I tried the same thing at first, and got the same error.  So I suspect Anna didn't really use that code either.  :-)

Dan

Daniel J. Nordlund
Washington State Department of Social and Health Services
Planning, Performance, and Accountability
Research and Data Analysis Division
Olympia, WA  98504-5204


> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On
> Behalf Of Rolf Turner
> Sent: Thursday, March 25, 2010 3:09 PM
> To: Joshua Wiley
> Cc: r-help at r-project.org
> Subject: Re: [R] Convert number to Date
> 
> 
> 
> Kind of off the thread a bit, but when I do:
> 
> > as.Date(40182)
> 
> I ***do not*** get "2080-01-06".  Instead I get an error:
> 
> Error in as.Date.numeric(40182) : 'origin' must be supplied
> 
> Am I the only user who gets picked on in this way, or does it
> happen to others as well?  The help on as.Date() clearly specifies
> that "origin" must be supplied.  So how come Anna got the result that
> she did?
> 
> > sessionInfo()
> R version 2.10.1 (2009-12-14)
> i386-apple-darwin8.11.1
> 
> locale:
> [1] en_NZ.UTF-8/en_NZ.UTF-8/C/C/en_NZ.UTF-8/en_NZ.UTF-8
> 
> attached base packages:
> [1] datasets  utils     stats     graphics  grDevices methods   base
> 
> other attached packages:
> [1] misc_0.0-12    fortunes_1.3-7 MASS_7.3-4
> 
> 	cheers,
> 
> 		Rolf Turner
> 
> On 26/03/2010, at 9:47 AM, Joshua Wiley wrote:
> 
> > Dear Anna,
> >
> > Rolf's explanation not withstanding, it has to do with differences in
> > how R and Excel treat dates.  If you use
> >
> > as.Date(40182, origin="1899-12-30")
> >
> > you will get the same date as Excel.  You can look at:
> >
> >
> http://office.microsoft.com/training/training.aspx?AssetID=RC102786151033&CTT=
> 6&Origin=RP102786121033
> >
> > For an official guide on how Excel dates are calculated.  Apparently,
> > Excel's calendar starts on 1 January 1900.  Why one has to use an
> > origin of 30 December 1899 in R...well, I suspect that gets back to
> > Rolf's explanation.
> >
> >
> > HTH,
> >
> > Josh
> >
> > On Thu, Mar 25, 2010 at 1:33 PM, anna <lippelanna24 at hotmail.com> wrote:
> >>
> >> Hello, I have a date value in excel: 1/4/2010 which in number format gives me
> >> 40182. When I read this with read.xls from R I get same 40182 so what I do
> >> is that I use the as.Date() function but here is what the as.Date() function
> >> returns me:
> >>> as.Date(40182)
> >> [1] "2080-01-06"
> >> Why don't I get the same thing as in excel?
> >> Thanks!
> 
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