[R] Sldf command returns negative value for date

[Sneha Bishnoi]

It works :) Thanks so much! I tried searching a lot but I guess i missed
this fact!


On Thu, Aug 14, 2014 at 4:35 PM, Gabor Grothendieck <ggrothendieck at gmail.com
> wrote:

> On Thu, Aug 14, 2014 at 3:47 PM, Sneha Bishnoi <sneha.bishnoi at gmail.com>
> wrote:
> > Hi All!
> >
> > I am trying to increment date column of data frame so as to merge it with
> > another data frame using sqldf:
> > my query is :
> > merge<-sqldf("select m.* ,e.* from mdata as m left join event as e on
> > date(m.Datest,'+1 day')=e.Start")
> >
> > The query returns null for all columns related to event table.
> > When I investigated further with query :
> > sqldf("select date(Datest,'+1 day')") from eventflight;")
> >  gives me -ve valued dates like : -4671-02-15
> >
> > However this works:
> > sqldf("select date(('2009-05-01'),'+1')")
> >
> > Dataframes are as follows:
> > mdata :
> > LOS Arrivals BookRange   Datest
> >  1     1283       0-4            2009-05-01
> >  1     1650       0-4            2009-05-08
> >  1     1302       5-9            2009-05-15
> >
> > event:
> >  Event.Name  Event.location          Start           End
> >  Birthday        Texas (US)           2009-05-02    2009-05-03
> >  Anni              Texas (US)          2009-05-09     2009-01-11
> >
> > What am I doing wrong?
>
> This is a FAQ.   See #4 here: http://sqldf.googlecode.com .
>
> The SQLite date function assumes its argument is a timestring but R
> "Date" class variables are transferred to SQLite as days since
> 1970-01-01 so just add 1.
>
>    sqldf("select * from mdata as m left join event on Datest+1 = Start")
>
>
>
> --
> Statistics & Software Consulting
> GKX Group, GKX Associates Inc.
> tel: 1-877-GKX-GROUP
> email: ggrothendieck at gmail.com
>



-- 
Sneha Bishnoi
+14047235469
H. Milton Stewart School of Industrial &  Systems Engineering
Georgia Tech

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