[R] merge 2 data frame based on more than 2 variables

[Simon Blomberg]

Wensui Liu wrote:
> Dear Lister,
>
> I understand merge() can be used to join 2 data frames based on 1 variable.
> But how about merge based on more than 2 variables?
>
> Thank you so much!
>
>   
Just specify the 2 (or more) variable names in a column vector for "by")

merge(dat1, dat2, by= c("VarA", "VarB"))

assuming both data frames have columns VarA and VarB.

-- 
Simon Blomberg, B.Sc.(Hons.), Ph.D, M.App.Stat.
Centre for Resource and Environmental Studies
The Australian National University
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