[R] help with for loop: new column giving count of observation for each SITEID

[William Dunlap]

Is this what you want?
  > withinGroupIndex <- function(group, ...) ave(integer(length(group)), group, ..., FUN=seq_along)
  > site <- c("A","A","C","D","C","A","B")
  > data.frame(site, index=withinGroupIndex(site))
    site index
  1    A     1
  2    A     2
  3    C     1
  4    D     1
  5    C     2
  6    A     3
  7    B     1

You can add more arguments if the groups depend on more than one value:
  > year <- rep(c(1985, 2012), c(4,3))
  > data.frame(site, year, index=withinGroupIndex(site, year))
    site year index
  1    A 1985     1
  2    A 1985     2
  3    C 1985     1
  4    D 1985     1
  5    C 2012     1
  6    A 2012     1
  7    B 2012     1

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 Meredith, Christy S -FS
> Sent: Tuesday, October 30, 2012 11:17 AM
> To: r-help at R-project.org
> Subject: [R] help with for loop: new column giving count of observation for each SITEID
> 
> 
> Hello,
> I think this is easy, but I can't seem to find a good way to do this in the R help. I have a list
> of sites, with multiple years of data for each site id. I want to create a new column that
> gives a number describing whether it is the 1st year ("1" ) the data was collected for the
> site, the second year ("2"), etc. I have different years for each siteid, but I don't care
> which year it was collected, just the order that it is in for that siteid.  This is what I have
> so far, but it doesn't do the analysis separately for each SiteID.
> 
> indexi<-indexg[order(indexg$SiteID,indexg$Yr),]
> 
> obs=0
> indexi=na.omit(indexi)
> for(i in 1:length(indexi$SiteID)){
> obs=obs+1
> indexi$obs[i]=obs
> }
> 
> 
> Thanks for any help you can give.
> 
> Christy Meredith
> USDA Forest Service
> Rocky Mountain Research Station
> PIBO Monitoring
> Data Analyst
> Voice: 435-755-3573
> Fax: 435-755-3563
> 
> 
> 
> 
> 
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