Skip to content

How to implement a "select distinct x, count(distinct y) ... group by x" for a data frame

4 messages · jim holtman, Gabor Grothendieck, Dimitri Shvorob

Dimitri Shvorob
# 
... 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.
jim holtman
# 
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:

  
    

      
      
    

  


  


      

    

    

      
      

        


  

        

      Gabor Grothendieck
    

    

      
      #
    

  


  

      
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: