[R] subsetting data by specified observation number

[Greg Snow]

Will failed.3 have each id exactly once? Or could it have multiple lines for a given id?

-- 
Gregory (Greg) L. Snow Ph.D.
Statistical Data Center
Intermountain Healthcare
greg.snow at imail.org
801.408.8111


> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of Linh Tran
> Sent: Saturday, March 05, 2011 11:56 AM
> To: r-help at r-project.org
> Subject: [R] subsetting data by specified observation number
> 
> Hi members,
> 
> I'd like to thank you guys ahead of time for the help. I'm kind of
> stuck.
> 
> I have a data frame with ID and position numbers:
> 1> head(failed.3)
>          id position
> 1  10000997        2
> 4  1000RW_M        2
> 15 1006RW_G        2
> 24 1012RW_M        3
> 28 10160917        2
> 30 1016RW_M       13
> 
> I'd like to use this to subset out a large dataset and keep only the
> observation number corresponding to the position number. So for
> example,
> ID 10000997 has 10 observations. I want to keep the 2nd one only.
> 
> 
> Thanks,
> 
> -linh
> 
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