
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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