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

[Meredith, Christy S -FS]

Not quite,
 I need it like this, a new number for each ordered year in the sequence within each site, regardless of what the years are,  and to retain the RchID column.

RchID	site	year	index
1	A	2002	1
2	A	2004	2
3	A	2005	3
4	B	2003	1
5	B	2006	2
6	B	2008	3
7	C	2002	1
8	C	2003	2
9	C	2004	3


Thanks so much for you help!

-----Original Message-----
From: William Dunlap [mailto:wdunlap at tibco.com] 
Sent: Tuesday, October 30, 2012 1:07 PM
To: Meredith, Christy S -FS; r-help at R-project.org
Subject: RE: [R] help with for loop: new column giving count of observation for each SITEID

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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