[R] creating a count variable in R

[William Dunlap]

Use cumsum() to count the change points:

> Date_var <- as.Date(rep(c("2011-02-04","2011-02-07","2011-01-29"),
c(2,3,1)))
> data.frame(Date_var, count=cumsum(c(TRUE,
Date_var[-1]!=Date_var[-length(Date_var)])))
    Date_var count
1 2011-02-04     1
2 2011-02-04     1
3 2011-02-07     2
4 2011-02-07     2
5 2011-02-07     2
6 2011-01-29     3

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com  

> -----Original Message-----
> From: r-help-bounces at r-project.org 
> [mailto:r-help-bounces at r-project.org] On Behalf Of JonC
> Sent: Thursday, March 03, 2011 1:58 PM
> To: r-help at r-project.org
> Subject: [R] creating a count variable in R
> 
> 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.
> 
> 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 
> 
> 
> --
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p3334288p3334288.html
> Sent from the R help mailing list archive at Nabble.com.
> 
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