[R] appending and merging data frames

[John Smith]

Hi Gerrit,

as I said in my original email, I already know both the
merge and the rbind commands, but I think that many
standard situations (I have given just a few) require
rather clumsy ad-hoc programming. So I was wondering
if there are any packages or existing code that would
make it easier to handle the diverse append/merge
tasks that tend to occur rather frequently.
For at least some of these tasks, other stats
packages, like Stata do provide out-of-the box
commands or command options.
Again, I just want to know if there is already some
package or code for this out there somewhere, especially
for appending tasks (automatically taking care of 
missing variables, renaming, data types etc.)
The RSiteSearch() function is helpful and came up
with slightly different versions of merge but nothing
for append.

John

> -----Original Message-----
> From: gerrit.eichner at math.uni-giessen.de
> Sent: Thu, 7 Feb 2013 16:57:13 +0100 (MET)
> To: johsmi9933 at inbox.com
> Subject: Re: [R] appending and merging data frames
> 
> Hello, John,
> 
> as a start take a look at
> 
> ?merge
> 
> And to (maybe) get a bit overwhelmed at first sight use
> 
> RSiteSearch( "merge")
> 
> 
>   Hth  --  Gerrit
> 
> On Thu, 7 Feb 2013, John Smith wrote:
> 
>> I know that the basic approach to append or merge data frames is using
>> the rbind and merge commands.
>> However, if I understand things correctly, for both commands one needs
>> to do quite some additional programming to get e.g. behavior as with the
>> Stata append and morge commands or to achieve some things which I think
>> users need quite frequently.
>> 
>> E.g. for appending, the data frame must have identical column names. In
>> order to rename columns or in order to add columns with missing values
>> if necessary, additional programming is needed.
>> For merging, all matches get combined, so it is not easily possible to
>> check for 1:1 or 1:n matches or limit the join to such kind of matches,
>> is it?
>> Those are just examples, there are a number of additional details that
>> would be useful to be able to control for merging/appending (maybe at
>> the expense of restricting the operation to just data frames).
>> 
>> So my question is: are there any packages or existing utility functions
>> which would provide append and merge functionality at a slightly higher
>> (user-friendly) level?
>> 
>> Although I am quite a noob, I would be prepared to give it a try and
>> program these myself, but I have the feeling that this must be so common
>> that maybe it would mean re-inventing the wheel?
>> 
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