[R] merge function

[John Kane]

Exactly what I thought too the first time I read ?merge. R sometimes has its own approach.

John Kane
Kingston ON Canada


> -----Original Message-----
> From: r-help at r-project.org
> Sent: Mon, 1 Jun 2015 14:47:07 +0000 (UTC)
> To: lists at dewey.myzen.co.uk, r-help at r-project.org
> Subject: Re: [R] merge function
> 
> I understood that by would take the intersection of names(x) and
> names(y), names(x) being the column names of x and names(y), column names
> of y.
> if x has 5 col and the col names of x are col1, col2... col5 and y has 3
> col and their names are col1, col2, col3, I thought that the merged data
> set will have 3 col, namely col1, col2, col3 but all 5 col, i.e. col1,
> col2... col5 are taken if nothing is specified for the by arg.
> Cheers,
> 
> 
> 
>      On Monday, June 1, 2015 4:32 PM, Michael Dewey
> <lists at dewey.myzen.co.uk> wrote:
> 
> 
> 
> 
> On 01/06/2015 14:46, carol white via R-help wrote:
>> Hi,By default the merge function should take the intersection of column
>> names
> 
>   (if this is understood from by = intersect(names(x), names(y)),
> 
> Dear Carol
> The by parameter specifies which columns are used to merge by. Did you
> understand it to be which columns are retained in the result?
> 
> Just a hunch, and if not then you need to give us a toy example.
> 
> 
> 
>   but it takes all columns. How to specify the intersection of column
> names?
> >  Thanks
>> Carol
>> 
>>     [[alternative HTML version deleted]]
>> 
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>> 
> 
> --
> Michael
> http://www.dewey.myzen.co.uk/home.html
> 
> 
> 
> 	[[alternative HTML version deleted]]
> 
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

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