[R] paste function by INDICES

[Phil Spector]

Massimiliano -
    Here's one way, assuming you wanted b to be the same 
length as a:

  df = transform(df,b=ave(as.character(df$a),df$ID,
                 FUN=function(a)paste(a,collapse='')))

If you just want one observation for each value of ID, you
could use

      aggregate(df$a,list(ID=df$ID),paste,collapse='')

 					- Phil Spector
 					 Statistical Computing Facility
 					 Department of Statistics
 					 UC Berkeley
 					 spector at stat.berkeley.edu



On Wed, 27 Apr 2011, Massimiliano Tripoli wrote:

> Dear all,
> I have the following  R dataframe:
>
>  set.seed(11)
>   (df <- data.frame(ID=rep(1:10,1:10),a=factor(sample(1:4,55,rep=T))    ))
>   where ID is an identification code.
>   I need to create a new variable "b" in which I would paste the full group
> of "a" variable according to ID variable.
>   For example for ID=2 "b" should be 13, for ID=3 "b" should be 114, and
> for ID=4 should be 1241.
>  How can I do that ?
>  Thank you for any advices,
>  Regards,
>   Massimiliano Tripoli
>
> 	[[alternative HTML version deleted]]
>
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