[R-sig-Geo] comparing raster and vector data with Grass/R
Edzer J. Pebesma
e.pebesma at geo.uu.nl
Wed Mar 7 22:33:28 CET 2007
Roger Bivand wrote:
> On Wed, 7 Mar 2007, Schmitt Thierry wrote:
>> I am struggling to overlay spatialLinesDataFrame and
>> SpatialGridDataFrame. The overlay method doesn't allow me to do so.
> There is no overlay method, you would need to write one, or interpolate
> points along your lines and overlay the resulting point object on the
There is an spsample method for lines which returns points, on random or
regular intervals. You could then overlay these points.
What exactly did you have in mind an overlay function for lines and
grids would do? In "Geographic information analysis" David O'Sullivan
and David Unwin suggest that any two types of spatial data can be
overlaid, leaving finding of examples as an example to the reader. I'm
still struggling with a few!
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