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

[William Dunlap]

For unsorted x, or for a factor x with unused levels,
  ave(integer(length(x)), x, FUN=seq_along) - 1
works.

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 PIKAL Petr
> Sent: Tuesday, September 04, 2012 4:08 AM
> To: Jon Toledo; r-help at r-project.org
> Subject: Re: [R] Create a function to number each repeated visit or measurements
> 
> 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
> > 	[[alternative HTML version deleted]]
> 
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