[R] Subsetting to unique values

[Chuck Cleland]

On 6/6/2008 9:35 AM, Emslie, Paul [Ctr] wrote:
> I want to take the first row of each unique ID value from a data frame.
> For instance
>> ddTable <-
> data.frame(Id=c(1,1,2,2),name=c("Paul","Joe","Bob","Larry"))
> 
> I want a dataset that is 
> Id	Name
> 1	Paul
> 2	Bob
> 
>> unique(ddTable)
> Will give me all 4 rows, and
>> unique(ddTable$Id) 
> Will give me c(1,2), but not accompanied by the name column.

ddTable <- data.frame(Id=c(1,1,2,2),name=c("Paul","Joe","Bob","Larry"))

!duplicated(ddTable$Id)
[1]  TRUE FALSE  TRUE FALSE

ddTable[!duplicated(ddTable$Id),]
   Id name
1  1 Paul
3  2  Bob

?duplicated

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-- 
Chuck Cleland, Ph.D.
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