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

[Gabor Grothendieck]

See ?replace to do it in one line.

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
>
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