[R] sqldf with date (class date) variables ?

[Gabor Grothendieck]

sqldf has some facilities for Date class but has no knowledge of date class.

See example 7b on home page: http://sqldf.googlecode.com
and here is a second example:

> DF <- data.frame(D = as.Date(c("21DEC2006","15DEC2006"), "%d%b%Y"))
> DF
           D
1 2006-12-21
2 2006-12-15
> sqldf("select * from DF")
           D
1 2006-12-21
2 2006-12-15


On Tue, Jan 6, 2009 at 1:09 PM,  <si.fu at ntlworld.com> wrote:
> Hello,
>
> I am having trouble with retrieving some data in queries involve with variables
> with data type "date". See the enclosed example:
>
> ll<-c("21DEC2006","15DEC2006")
> ss<-data.frame(ll)
> ss<-transform(ss,ll=as.date(as.character(ll)))
> (ss)
>     ll
> 1 17156
> 2 17150
>
> tt<-sqldf("select ll from ss")
>
> (tt)
>>
>  ll
> 1 NA
> 2 NA
>
>> str(ss)
> 'data.frame':   2 obs. of  1 variable:
>  $ ll:Class 'date'  int [1:2] 17156 17150
>
>> str(tt)
> 'data.frame':   2 obs. of  1 variable:
>  $ ll:Class 'date'  int [1:2] NA NA
>
> So all the elements of ll (of tt) has been converted into NA. Is there anyway that I can query the variables with "date" data type using sqldf?
>
>
> Many Thanks,
>
> Si.
>
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