On Feb 7, 2013, at 9:12 AM, John Smith wrote:
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.
The sqldf package provides an interface to popular database drivers. I
do not think your question provides enough specificity to go much
further. You say Stata provides ... something... but you do not really
explain what that something is. My efforts to understand the Stata
documentation for the egen command left me shaking my head in
disbelief at its opacity, and caused me to appreciate further the
efforts of the R developers to make our help system available. The
most productive approach would be to present a simple example in R code.
--
David.
John
-----Original Message-----
From: gerrit.eich...@math.uni-giessen.de
Sent: Thu, 7 Feb 2013 16:57:13 +0100 (MET)
To: johsmi9...@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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