R help - Apr 2008 - filtering out duplicates & creating a dataframe with unique id

Hello,

I am working on a dataframe that contains a number of duplicates (e.g 
a person may have more than one court appearance). There are 539 
rows. If I run the code:

 > length(unique(Feb25$ Patient.Id))

this indicates there are 508 unique individuals. I have been unable 
to work out how to filter out rows where there is a duplicate id so 
that the resulting dataframe consists only of the one id per person, 
and this id, is the first one thartappears.

I was also interested in creating a data frame that consisted of 
these removed duplicates.

  Any assistance with the code to do this is much appreciated,


regards

Bob Green

try the following:

dat <- data.frame(
    id = gl(10, 5),
    y = rnorm(50),
    time = rep(1:5, 10),
    sex = gl(2, 25, labels = c("male", "female")),
    age = round(rep(runif(10, 18, 55), each = 5), 1)
)

dat[tapply(row.names(dat), dat$id, head, n = 1), ]
dat[!duplicated(dat$id), ]


I hope it helps.

Best,
Dimitris

----
Dimitris Rizopoulos
Biostatistical Centre
School of Public Health
Catholic University of Leuven

Address: Kapucijnenvoer 35, Leuven, Belgium
Tel: +32/(0)16/336899
Fax: +32/(0)16/337015
Web: http://med.kuleuven.be/biostat/
     http://www.student.kuleuven.be/~m0390867/dimitris.htm


----- Original Message ----- 
From: "Bob Green" <bgreen at dyson.brisnet.org.au>
To: <r-help at r-project.org>
Sent: Tuesday, April 01, 2008 11:37 AM
Subject: [R] filtering out duplicates & creating a dataframe with 
unique id

> Hello,
>
> I am working on a dataframe that contains a number of duplicates 
> (e.g
> a person may have more than one court appearance). There are 539
> rows. If I run the code:
>
> > length(unique(Feb25$ Patient.Id))
>
> this indicates there are 508 unique individuals. I have been unable
> to work out how to filter out rows where there is a duplicate id so
> that the resulting dataframe consists only of the one id per person,
> and this id, is the first one thartappears.
>
> I was also interested in creating a data frame that consisted of
> these removed duplicates.
>
>  Any assistance with the code to do this is much appreciated,
>
>
> regards
>
> Bob Green
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide 
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
> 

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