[R] ifelse and dates do not work together: What workaround?

[Peter Dalgaard]

Gabor Grothendieck wrote:
> See ?replace to do it in one line.
>   
Also, don't miss the bleeding obvious (or so one might think...):

> z <- ifelse(TRUE, as.Date("2007-01-01"), as.Date("2007-01-02"))
> class(z) <- "Date"
> z
[1] "2007-01-01"

In the special case of censoring, you can also get away with

end <- pmin(died, endofstudy, na.rm=TRUE)

(This has the side effect of eliminating deaths recorded after end of
follow-up, which is generally a Good Thing.)

> On 9/27/07, Farrel Buchinsky <fjbuch at gmail.com> wrote:
>   
>> I encountered the above problem. I went to the help files and
>> discovered the reason why. My insight as to why it was happening did
>> not immediately provide me with a solution by which I could accomplish
>> what I needed to do. I turned to the help archive. I encountered a
>> thread on which somebody pointed this problem out and was mildly
>> castigated for not having looked at the help file. Alas no workaround
>> was provided.
>>
>> ifelse(test, yes, no) is wonderful since it works well in a dataframe
>> but only if yes and no are something simple, such as a numeric vector.
>> But if yes and no are dates then it does not work.
>>
>> My workaround was quite inelegant.
>> Instead of the elegance of
>> official.date<-ifelse(is.na(x),dateyes,dateno)
>>
>> I resorted to conditional indexing.
>> official.date<-dateno #only apporopriate when x is not missing
>> official.date[is.na(x)]<-dateyes[is.na(x)]
>>
>>
>> Original thread:
>> On Sat, 3 Jun 2006, ivo welch wrote:
>>
>>     
>>> I wonder if this is an intentional feature or an oversight.
>>>       
>> These are documented properties of the functions you are using.
>>
>>     
>>> in some column summaries or in ifelse operations, apparently I am losing
>>> the date property of my vector.
>>>
>>>       
>> ...
>>     
>>>> ifelse( is.na(c), e, c )
>>>>         
>>> [1] 4017 4048 4076   # date property is lost
>>>       
>> As documented. From ?ifelse:
>>
>> Value:
>>
>>      A vector of the same length and attributes (including class) as
>>      'test' and data values from the values of 'yes' or 'no'.  The mode
>>      of the answer will be coerced from logical to accommodate first
>>      any values taken from 'yes' and then any values taken from 'no'.
>>
>> Note that the class is taken from 'test'.
>>
>>     
>>> PS: this time I do not need help.  I can write my code around this.
>>>       
>> Help in pointing you to the posting guide and its recommended reading of
>> the help page might still be helpful.
>>
>>
>>
>>
>>
>> --
>> Farrel Buchinsky
>> GrandCentral Tel: (412) 567-7870
>>
>> ______________________________________________
>> R-help at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>
>>     
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>   


-- 
   O__  ---- Peter Dalgaard             Øster Farimagsgade 5, Entr.B
  c/ /'_ --- Dept. of Biostatistics     PO Box 2099, 1014 Cph. K
 (*) \(*) -- University of Copenhagen   Denmark          Ph:  (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)                  FAX: (+45) 35327907