All fixed, thanks. I needed to install the "Spring Dance” version of R. Not quite sure what was wrong previously, but it works now!

Cheers
Justin


On Jun 3, 2014, at 3:20 PM, Alaba Boluwade <alaba.boluwade@mail.mcgill.ca> wrote:

>> r <- raster(ncol=36, nrow=18)
>> r[] <- 1:ncell(r)
>> 
>> ###############################
>> # extract values by cell number
>> ###############################
>> extract(r, c(1:2, 10, 100))
> Error in (function (classes, fdef, mtable)  :
>  unable to find an inherited method for function �extract� for signature �"RasterLayer"�
>> s <- stack(r, sqrt(r), r/r)
>> extract(s, c(1, 10, 100), layer=2, n=2)


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