[R-sig-Geo] Alternative to zonal for large images

[Forrest Stevens]

On Mon, Feb 11, 2013 at 10:44 PM, Ned Horning <horning at amnh.org> wrote:
> Hi - Are there alternatives to using the raster package "zonal" function
> for
> large images when using functions for the "stat" parameter?

I would be interested to know as well.  I have found both extract and
zonal to be unworkably slow over large datasets.  As a workaround I
currently am using RPyGeo to run zonal statistics using the ArcGIS
GeoProcessing environment.  I'd like to keep it all in R without the
overhead of invoking the ArcGIS environment, but as of right now it
takes a fraction of the time to jump through those hoops, even with
moderately sized raster and polygon datasets.

I hope this causes no offense to Robert and Jacob regarding the raster
package... It's truly indispensable and makes R a joy to work with for
most raster-based tasks.. But I think there's room for improvement
somewhere along that analysis chain, with a bottleneck that can
hopefully be bypassed at some point soon (I haven't had time to dig
into the source but maybe one day!)

Sincerely,
Forrest Stevens

--
Ph.D. Candidate, QSE3 IGERT Fellow
Department of Geography
Land Use and Environmental Change Institute
University of Florida
www.clas.ufl.edu/users/forrest