[R-sig-Geo] How to overlay two rasters limiting the spatial domain

[Robert Hijmans]

Thiago, 
You can use the 'crop' function. 
Best, Robert


>  Dear R colleagues,
>
>  Currently, I am working with the vegetation map published by SAGE
> (http://www.sage.wisc.edu/download/potveg/global_potveg.html). This map is
> published in netcdf and I can easily load it into R using the package
> "raster".
>
>  But I have found another vegetation map (also netcdf, same resolution)
> which is more realistic to my work region. Thus, what I need to do is
> overlay the two maps, but using a clip feature (i.e. a shapefile of South
> America) as a delimiter to this operation, in order to capture the
> information of the newest map.
>
>  I am trying to use the "overlay" function of raster package, but
> apparently it isn't possible (or I am missing something) to use a clip
> feature to restrain the spatial domain of the operation.
>
>  Any tips on how to do this? Below is the code I am using.
>
>  Best wishes,
>
>  Thiago Veloso.
>
> #Loading required packages
> library(raster)
> library(maptools)
>
> #Loading SAGE vegetation map
> vegmap<-raster("C:/temp/vegmap_ibis/data/vegtype.nc")
>
> #Loading new vegetation map
> new_vegmap<-raster("C:/temp/vegmap_ibis/data/new_vegtype.nc")
>
> #Loading SA shapefile
> south_america<-readShapePoly("C:/temp/vegmap_ibis/shapes/southamerica.shp")
>
> #Replacing the original map with the modified one
> result<-overlay(vegmap,new_vegmap,fun=function(x){x}) #this is where I
> stop - I don't know how to use the shapefile as a clip feature in this
> function...
>


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