[R] Create a function to number each repeated visit or measurements

[PIKAL Petr]

Hi

You did not provided any suitable data. 

x<-sort(sample(letters[1:5], 50, rep=T))
unlist(lapply(split(x,x), function(x) (1:length(x))-1))

gives you a vector of indices from 0 to n for sorted vector x.

Regards
Petr


> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of Jon Toledo
> Sent: Tuesday, September 04, 2012 7:59 AM
> To: r-help at r-project.org
> Subject: [R] Create a function to number each repeated visit or
> measurements
> 
> 
> Hi dear R list members,
> I am trying to create a numerical variable that tracks the
> visits/entries that a subject has had. For example having a database of
> repeated serial measurements that are ordered by subject and time. So I
> would get a variable that says 0 for baseline visit/measurement, 1 for
> the second etc.
> In my case the unique identifier for each subject is AreaID Will the
> following code I can number the visits as long as I create as many
> lines as visits.
> But there is probably a way of coding a function or maybe there is
> already a function.
> DUP<-rep(0,length(AreaID))DUP[2:length(DUP)]<-
> sapply(2:(length(AreaID),function(x) ifelse(AreaID[x]==AreaID[x-
> 1],1,DUP[x]))DUP[3:length(DUP)]<-sapply(3:(
> length(AreaID),function(x) ifelse(AreaID[x]==AreaID[x-2],2,DUP[x]))
> My Guess was:
> AddLag<-function(x) {		DUP<-c(rep(0,length(x)))	for (i in
> 1:(max(as.numeric(GraphArtDB$Measure))+2)){
> 	DUP[(i+1):length(x)]<-sapply(((i+1):length(x)),function(x)
> ifelse(x[i]==x[x-i],i,DUP[x]))	}		return(DUP)		}
> 
> But it didn´t work.
> Any suggestions?
> 
> Thanks in advance
> 
> J ToledoUPennUSA
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