R help - Jan 2010 - How to implement a "select distinct x, count(distinct y) ... group by x" for a data frame

... Being an R newbie, I can only think of extracting distinct x values with
unique, looping over them, extracting matching rows from the original data
frame, applying table, and recording the size of table's output alongside
the x value being checked. Is there a more elegant way? 

Thank you.
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Yes.

?sqldf
?split
?lapply

But unless you provide commented, minimal, self-contained,
reproducible code, it is hard to say how to proceed to a solution.

On Sat, Jan 23, 2010 at 5:46 PM, Dimitri Shvorob
<dimitri.shvorob at gmail.com> wrote:
>
> ... Being an R newbie, I can only think of extracting distinct x values
with
> unique, looping over them, extracting matching rows from the original data
> frame, applying table, and recording the size of table's output
alongside
> the x value being checked. Is there a more elegant way?
>
> Thank you.
> --
> View this message in context:
http://n4.nabble.com/How-to-implement-a-select-distinct-x-count-distinct-y-group-by-x-for-a-data-frame-tp1288418p1288418.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> R-help at r-project.org mailing list
> 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.
>


-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem that you are trying to solve?

Regarding your subject, the sqldf package on CRAN allows you to apply
SQL statements directly to R data frames.  http://sqldf.googlecode.com

On Sat, Jan 23, 2010 at 5:46 PM, Dimitri Shvorob
<dimitri.shvorob at gmail.com> wrote:
>
> ... Being an R newbie, I can only think of extracting distinct x values
with
> unique, looping over them, extracting matching rows from the original data
> frame, applying table, and recording the size of table's output
alongside
> the x value being checked. Is there a more elegant way?
>
> Thank you.
> --
> View this message in context:
http://n4.nabble.com/How-to-implement-a-select-distinct-x-count-distinct-y-group-by-x-for-a-data-frame-tp1288418p1288418.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> R-help at r-project.org mailing list
> 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.
>

sqldf answered my prayers and more. Thanks a lot!
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