[R] Remove single entries

[Chuck Cleland]

On 9/28/2009 12:03 PM, Raymond Danner wrote:
> Dear Community,
> 
> I have a data set with two columns, bird number and mass.  Individual birds
> were captured 1-13 times and weighed each time.  I would like to remove
> those individuals that were captured only once, so that I can assess mass
> variability per bird.  I¹ve tried many approaches with no success.  Can
> anyone recommend a way to remove individuals that were captured only once?
> 
> Thanks,
> Ray

  How about something like this?

DF <- data.frame(BIRD = rep(1:10, c(1,1,2,10,5,6,7,1,8,9)),
                 MASS = rnorm(50,50,10))

DF$NOBS <- with(DF, ave(MASS, BIRD, FUN=length))

subset(DF, NOBS > 1)

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-- 
Chuck Cleland, Ph.D.
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