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as.Date without "origin"

9 messages · Dan Dalthorp, Peter Dalgaard, Johannes Rauh +3 more

Original
Dan Dalthorp
# 
The new (2022-10-11 r83083 ucrt) as.Date function returns a date rather than an error when called without "origin" specified.

# previous versions of R
as.Date(0)
# Error in as.Date.numeric(0) : 'origin' must be supplied

# new:
as.Date(0)
# [1] "1970-01-01"

This is at odds with the help file, which gives:

origin

aDateobject, or something which can be coerced byas.Date(origin, ...)to such an object.

And:
as.Datewill accept numeric data (the number of days since an epoch), butonlyiforiginis supplied.

The behavior described in the help file and implemented in previous versions seems more reasonable than returning a date with an arbitrary "origin". In any case, in the r-devel there is a mismatch between the function and its description.

-Dan
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Spencer Graves
# 
I've felt that "as.Date" should default to origin "1970-01-01", so I 
added a modification to Ecfun:


Ecfun::as.Date1970(0)


	  If R-devel chose to change the default on this, I would happily 
deprecate Ecfun::as.Date1970 in favor of base::as.Date ;-)


	  I would therefore support changing the documentation to match the new 
behavior.


	  Spencer Graves
On 11/2/22 7:30 AM, Dan Dalthorp via R-devel wrote:
Dan Dalthorp
# 
I don't see a compelling rationale for changing the default behavior as.Date to deviate from the wholly reasonable status quo of "as.Date will accept numeric data (the number of days since an epoch), but only if origin is supplied." That has been the expectation for a long, long time. 

In any case, the manual should match the behavior.

-DHD




------- Original Message -------
On Wednesday, November 2nd, 2022 at 6:20 AM, Spencer Graves <spencer.graves at prodsyse.com> wrote:

            

      
      
      
    

        

      
      
    

  
  


  

    

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      Peter Dalgaard
    

    

      
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This is in R-devel, mind you, i.e., unreleased and quite possibly unfinished work.

No released version of R does this. E.g.,

            

      
      
      
    

        
Error in as.Date.numeric(0) : 'origin' must be supplied

            

      
      
      
    

        
_                                          
platform       x86_64-apple-darwin21.6.0                  
arch           x86_64                                     
os             darwin21.6.0                               
system         x86_64, darwin21.6.0                       
status         Patched                                    
major          4                                          
minor          2.2                                        
year           2022                                       
month          11                                         
day            02                                         
svn rev        83236                                      
language       R                                          
version.string R version 4.2.2 Patched (2022-11-02 r83236)
nickname       Innocent and Trusting

            

      
      
      
    

        

      
      
    

            

      
      
      
    

        

      
      
    

        

  
    

      
      
    

  


  


      

    

    

      
      

        


  

        

      Dan Dalthorp
    

    

      
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Of course. But the broken as.Date in R-devel breaks one of my packages, so I'm getting threats of the package being removed from CRAN in a few days if the breakage is not resolved.

DHD




------- Original Message -------

        
On Wednesday, November 2nd, 2022 at 8:30 AM, peter dalgaard <pdalgd at gmail.com> wrote:

        

            

      
      
      
    

        

      
      
    

            

      
      
      
    

        

      
      
    

            

      
      
      
    

  
  


  

    

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      Johannes Rauh
    

    

      
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Dear all,

I would throw in my vote to have origin = "1970-01-01" as a default in as.Date().  Why?  Well, in fact, the "converse" function as.numeric() does have an implicit default:

            

      
      
      
    

        
[1] 19298

In fact, as.numeric seems to not even have a method for class "Date", and so as.numeric() does not even have an argument "origin" or the like.

In any case, when using Date objects, it may happen that the result is of clas numeric. For example:

            

      
      
      
    

        
[1] 19298

So, in order to transform the result back to class "Date" using as.Date(), I always need to remember the universal default origin 1970-01-01 and I need to write it out explicitly.

I find that rather inconvenient, and so having the default origin as a default would make very much sense to me here.

Of course, for that particular example, it would also help me if ifelse() would properly handle Date vectors.

Best
Johannes

            

      
      
      
    

        

      
      
    

            

      
      
      
    

        

      
      
    

  
  


  


      

    

    

      
      

        


  

        

      Rui Barradas
    

    

      
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?s 20:47 de 02/11/2022, Johannes Rauh escreveu:

            

      
      
      
    

        

      
      
    

            

      
      
      
    

        

      
      
    

            

      
      
      
    

        

      
      
    

        
Hello,

ifelse does properly handle Date objects. From its documentation:


Usage
ifelse(test, yes, no)
[...]
Value
A vector of the same length and attributes (including dimensions and 
"class") as test and data values from the values of yes or no.


In your example test = TRUE and yes = Sys.Date() so the return value is


class(ifelse(TRUE, Sys.Date(), Sys.Date() + 1))
# [1] "numeric"

class(ifelse(TRUE, Sys.Date(), Sys.Date() + 1L))
# [1] "numeric"


This is expected behavior.
I was expecting class "integer", not "numeric" but this too is 
documented in ?Dates section Details 2nd paragraph.


It is intended that the date should be an integer, but this is not 
enforced in the internal representation. Fractional days will be ignored 
when printing. It is possible to produce fractional days via the mean 
method or by adding or subtracting (see Ops.Date).


Hope this helps,

Rui Barradas

  
  


  


      

    

    

      
      

        


  

        

      Spencer Graves
    

    

      
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On 11/2/22 5:32 PM, Rui Barradas wrote:

            

      
      
      
    

        

      
      
    

            

      
      
      
    

        

      
      
    

            

      
      
      
    

        

      
      
    

            

      
      
      
    

        
I routinely use fractional days with class "Date".  I hope I can 
continue to do so.  Thanks, Spencer Graves

            

      
      
      
    

        

      
      
    

  
  


  


      

    

    

      
      

        


  

        

      Simon Urbanek
    

    

      
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Dan,

as.Date() and as.POSIXct() have been updated to allow replacement of the hidden functions .POSIXct() and .Date() which were the only way to correctly convert the numeric representation of the objects as Johannes explained. Given that this is a very common operation (especially with POSIXct) it makes sense to not rely on hidden functions and will allow us to possibly deprecate them. And as Peter pointed out, this is R-devel so manuals won't be necessarily updated until the full functionality is implemented and this is part of a larger overhaul of the date/time functions which has not been finished yet.

Cheers,
Simon