[R] creating a count variable in R

[David Winsemius]

On Mar 3, 2011, at 3:58 PM, JonC wrote:

> Hi R helpers,
>
> I'm trying to create a count in R , but as there is no retain  
> function like
> in SAS I'm running into difficulties.

Your data is not cut-pastable as presented but this should work:

 > dfrm$count_var <- ave(as.numeric(dfrm$Date_var), dfrm$Date_var,  
FUN=seq_along)
 > dfrm
      Date_var count_var
1  01/01/2011         1
2  01/01/2011         2
3  02/01/2011         1
4  02/01/2011         2
5  02/01/2011         3
6  02/01/2011         4
7  03/01/2011         1
8  03/01/2011         2
9  03/01/2011         3
10 03/01/2011         4
11 03/01/2011         5
12 03/01/2011         6
13 03/01/2011         7


>
> I have the following :
>
> Date_var                           and wish to obtain      Date_var
> Count_var
> 01/01/2011                                                        
> 01/01/2011
> 1
> 01/01/2011                                                        
> 01/01/2011
> 2
> 02/01/2011                                                        
> 02/01/2011
> 1
> 02/01/2011                                                        
> 02/01/2011
> 2
> 02/01/2011                                                        
> 02/01/2011
> 3
> 02/01/2011                                                        
> 02/01/2011
> 4
> 03/01/2011                                                        
> 03/01/2011
> 1
> 03/01/2011                                                        
> 03/01/2011
> 2
> 03/01/2011                                                        
> 03/01/2011
> 3
> 03/01/2011                                                        
> 03/01/2011
> 4
> 03/01/2011                                                        
> 03/01/2011
> 5
> 03/01/2011                                                        
> 03/01/2011
> 6
> 03/01/2011                                                        
> 03/01/2011
> 7
>
> As can be seen above the count var is re initialised every time a  
> new date
> is found. I hope this is easy.
>
> Many thanks in advance for assistance. It is appreciated.
>
> Cheers
>
> Jon
>
>
> --
> View this message in context: http://r.789695.n4.nabble.com/creating-a-count-variable-in-R-tp3334288p3334288.html
> Sent from the R help mailing list archive at Nabble.com.
>
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David Winsemius, MD
Heritage Laboratories
West Hartford, CT