[R] Merging data.table and data.frame

[peter dalgaard]

On 13 May 2014, at 14:34 , Abhinaba Roy <abhinabaroy09 at gmail.com> wrote:

> Hi R-helpers,
> 
> I am trying the following code in R
> 
> merge(x=Master1,y=demo_dtls,by.x=c("ID_CASE","ts"),by.y=c("ID_CASE","TS_EVENT"))
> 
> where,
> 
> class(demo_dtls$TS_EVENT)
> [1] "POSIXct" "POSIXt"
> class(Master1$ts)
> [1] "POSIXct" "POSIXt"
> 
> and
> 
>> class(Master1)[1] "data.table" "data.frame"> class(demo_dtls)[1] "data.frame"
> 
> 
> But I am getting the following error
> 
> Error in merge.data.table(x = Master1, y = demo_dtls, by.x = c("ID_CASE",  :
>  Can not match keys in x and y to automatically determine appropriate
> `by` parameter. Please set `by` value explicitly.
> 
> Why am I getting this error?

You are using merge.data.frame syntax for merge.data.table. The latter knows about by=, but not by.x= and by.y= (so presumably you need to rename variables in x or y).

- Peter


> Any help will be appreciated
> 
> 
> -- 
> Regards
> Abhinaba Roy
> 
> 	[[alternative HTML version deleted]]
> 
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-- 
Peter Dalgaard, Professor
Center for Statistics, Copenhagen Business School
Solbjerg Plads 3, 2000 Frederiksberg, Denmark
Phone: (+45)38153501
Email: pd.mes at cbs.dk  Priv: PDalgd at gmail.com