[R] transforming factor back to numbers

[Rainer M Krug]

Hi

I generate a new dataframe by doing:

npl.agg <- aggregate(npl$DensPlants, list(year=npl$year, sim=npl$sim), 
mean, na.rm=TRUE )

Now I want to plot it by using

coplot(npl.agg$x ~ npl.agg$year | npl.agg$sim, type="l")

but, as npl.agg$year is seen as a factor, the order of the points on the 
x-axis (time axis) does not follow the numerical sorting 1...100, but 
rather the text sorting of the factor npl.agg$year

Is there any way that I can 'defactor' npl.agg$year so that I have again 
the numerical values for year?

Thanks

Rainer

-- 
Rainer M. Krug, Dipl. Phys. (Germany), MSc Conservation
Biology (UCT)

Department of Conservation Ecology and Entomology
University of Stellenbosch
Matieland 7602
South Africa

Tel:		+27 - (0)72 808 2975 (w)
Fax:		+27 - (0)21 808 3304
Cell:		+27 - (0)83 9479 042

email:	RKrug at sun.ac.za
       	Rainer at krugs.de