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Aggregate factor names

5 messages · Gabor Grothendieck, Michael Lawrence, Brian Ripley

Original
Michael Lawrence
# 
Hi all,

A suggestion derived from discussions amongst a number of R users in  
my research group: set the default column names produced by aggregate 
() equal to the names of the objects in the list passed to the 'by'  
object.

ex. it is annoying to type

with(
	my.data
	,aggregate(
		my.dv
		,list(
			one.iv = one.iv
			,another.iv = another.iv
			,yet.another.iv = yet.another.iv
		)
		,some.function
	)
)

to yield a data frame with names = c 
('one.iv','another.iv','yet.another.iv','x') when this seems more  
economical:

with(
	my.data
	,aggregate(
		my.dv
		,list(
			one.iv
			,another.iv
			,yet.another.iv
		)
		,some.function
	)
)

--
Mike Lawrence
Graduate Student, Department of Psychology, Dalhousie University

Website: http://memetic.ca

Public calendar: http://icalx.com/public/informavore/Public

"The road to wisdom? Well, it's plain and simple to express:
Err and err and err again, but less and less and less."
	- Piet Hein
Gabor Grothendieck
# 
You can do this:

aggregate(iris[-5], iris[5], mean)
On 9/27/07, Mike Lawrence <Mike.Lawrence at dal.ca> wrote:
Michael Lawrence
# 
Understood, but my point is that the naming I suggest should be the  
default. One should not be 'punished' for being explicit in calling  
aggregate.
On 27-Sep-07, at 1:06 PM, Gabor Grothendieck wrote:

            

      
      
      
    

        

      
      
    

        
--
Mike Lawrence
Graduate Student, Department of Psychology, Dalhousie University

Website: http://memetic.ca

Public calendar: http://icalx.com/public/informavore/Public

"The road to wisdom? Well, it's plain and simple to express:
Err and err and err again, but less and less and less."
	- Piet Hein

  
  


  


      

    

    

      
      

        


  

        

      Gabor Grothendieck
    

    

      
      #
    

  


  

      
You can do this too:

aggregate(iris[-5], iris["Species"], mean)

or this:

with(iris, aggregate(iris[-5], data.frame(Species), mean))

or this:

attach(iris)
aggregate(iris[-5], data.frame(Species), mean)

The point is that you already don't have to write x = x.  The only
reason you are writing it that way is that you are using list instead
of data.frame.  Just use data.frame or appropriate indexing as shown.

        
On 9/27/07, Mike Lawrence <Mike.Lawrence at dal.ca> wrote:

            

      
      
      
    

        

      
      
    

            

      
      
      
    

  
  


  


      

    

    

      
      

        


  

        

      Brian Ripley
    

    

      
      #
    

  


  

      
You seem to be assuming that the argument 'by' to the "data frame" method 
of aggregate() is a call to list() with arguments which are names (and 
evaluate to factors).

When aggregate.data.frame comes to be called, the 'by' argument is a 
promise to the actual argument.  In your example the actual argument is 
the call (in a readable layout)

list(one.iv, another.iv, yet.another.iv)

but that is one of a very large number of possibilities for 'by'.  Trying 
to produce reasonable names for unnamed arguments is hard enough (see 
?cbind), but trying to deduce reasonable names for the elements of a list 
argument is one step further up the chain.  Further, if we did that, 
people who wanted the documented behaviour would not longer be able to get 
it.

I think what you want is a function that takes unnamed arguments and 
returns a named list, to replace your usage of list().  That's not so very 
hard to do, not least as in this context data.frame() will do the job.
So to extend the example on the help page

            

      
      
      
    

        
by1  by2 v1 v2
1    1   95  5 55
2    2   95  7 77
3    1   99  5 55
4    2   99 NA NA
5  big damp  3 33
6 blue  dry  3 33
7  red  red  4 44
8  red  wet  1 11

However, note that the grouping variables need NOT be factors, and this 
has made them so.  So you may want to look at data.frame() and
write list_with_names() to do just that.

        
On Thu, 27 Sep 2007, Mike Lawrence wrote: