[R] Identifying last record in individual growth data over different time intervalls

[Rainer M. Krug]

Hi Chris

Chris Stubben wrote:
>> Finally I would like to have a data.frame t2 which only contains the 
>> entries of the last measurements.
>>
> 
> You could also use aggregate to get the max year per plate then join that back
> to the original dataframe using merge on year and plate (common columns in both
> dataframes).
> 

Thanks for the idea to use aggregate and merge - as I like SQL, this 
seems to be a nice approach.

Rainer

> 
> 
> x<-data.frame(id=(1:8), plate=c(15,15,15,20,20,33,43,43),
> year=c(2004,2005,2006,2004,2005,2004,2005,2006), 
> height=c(0.40,0.43,0.44,0.90,0.94,0.15,0.30,0.38))
> 
> merge(x, aggregate(list(year=x$year), list(plate=x$plate), max))
> 
> 
>   plate year id height
> 1    15 2006  3   0.44
> 2    20 2005  5   0.94
> 3    33 2004  6   0.15
> 4    43 2006  8   0.38
> 
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