[R] Loops to assign a unique ID to a column

[ONKELINX, Thierry]

Dear Chandra,

You're on the wrong track. You don't need for loops as you can do this vectorised.

as.numeric(interaction(data$Groups, data$Dates, drop = TRUE))

Best regards,

Thierry

> -----Oorspronkelijk bericht-----
> Van: r-help-bounces op r-project.org [mailto:r-help-bounces op r-project.org]
> Namens Chandra Salgado Kent
> Verzonden: dinsdag 2 augustus 2011 9:12
> Aan: r-help op r-project.org
> Onderwerp: [R] Loops to assign a unique ID to a column
> 
> Dear R help,
> 
> 
> 
> I am fairly new in data management and programming in R, and am trying to
> write what is probably a simple loop, but am not having any luck. I have a
> dataframe with something like the following (but much bigger):
> 
> 
> 
> Dates<-c("12/10/2010","12/10/2010","12/10/2010","13/10/2010",
> "13/10/2010", "13/10/2010")
> 
> Groups<-c("A","B","B","A","B","C")
> 
> data<-data.frame(Dates, Groups)
> 
> 
> 
> I would like to create a new column in the dataframe, and give each distinct
> date by group a unique identifying number starting with 1, so that the resulting
> column would look something like:
> 
> 
> 
> ID<-c(1,2,2,3,4,5)
> 
> 
> 
> The loop that I have started to write is something like this (but doesn't work!):
> 
> 
> 
> data$ID<-as.number(c())
> 
> for(i in unique(data$Dates)){
> 
>   for(j in unique(data$Groups)){ data$ID[i,j]<-i
> 
>   i<-i+1
> 
>   }
> 
> }
> 
> 
> 
> Am I on the right track?
> 
> 
> 
> Any help on this is much appreciated!
> 
> 
> 
> Chandra
> 
> 
> 	[[alternative HTML version deleted]]
> 
> ______________________________________________
> R-help op 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.