[R-sig-Geo] help to obtain the list of the ID

[Paul Hiemstra]

gianni lavaredo schreef:
> Thanks in advice for your time,
>
> Sorry for this simple question I am searching a function or a method to
> obtain the list of the ID. I tryed sever combination like manual or in R
> wiki
>
>
> mfDF <- data.frame(
>   ID =c(1,1,1,1,2,2,2,2,2,3,3,3,3,3,3,3,3),
>   value =c(2,12,25,50,100,200,6,12,50,25,50,50,6,8,90,5,8))
>
> like this
>
>   
> 1 2 3
>
> Thanks and sorry
>
> Gianni
>
> 	[[alternative HTML version deleted]]
>
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>   
Hi,

Because ID is a categorical value, it is good to make it a factor (R 
type for categories). Then it is also quite easy to get the levels:

 mfDF <- data.frame(
   ID =as.factor(c(1,1,1,1,2,2,2,2,2,3,3,3,3,3,3,3,3)),
   value =c(2,12,25,50,100,200,6,12,50,25,50,50,6,8,90,5,8))
# Get a list of the possible ID's
levels(mfDF$ID)

cheers,
Paul

-- 
Drs. Paul Hiemstra
Department of Physical Geography
Faculty of Geosciences
University of Utrecht
Heidelberglaan 2
P.O. Box 80.115
3508 TC Utrecht
Phone:  +3130 274 3113 Mon-Tue
Phone:  +3130 253 5773 Wed-Fri
http://intamap.geo.uu.nl/~paul