[R-sig-Geo] converting grid objects to spatial polygon objects and export as shapefile

Tom Gottfried tom.gottfried at tum.de
Mon Sep 19 13:16:52 CEST 2011



over(R1000m, raster_data)

wich should give you the desired result. overlay() is deprecated.


Am 19.09.2011 12:11, schrieb didimayr:
> Dear all,
> I am trying to do the same as above in: “converting grid objects to spatial
> polygon objects and export as shapefile , Dec 10, 2009; 3:17am” with my own
> data, however I do not come to any useful result. My aim is to get a
> shapefile with polygons with an additional column including the overlayed
> raster data. Maybe someone has an idea or some hints:
> I have a shapefile converted into a SpatialPolygonsDataFrame (“R1000m”) and
> a asc-rasterfile converted into a SpatialPointsDataFrame(“raster_data”)
>    overlay_1<- overlay(raster_data, R1000m)
> result: overlay_1 is an integer, similar to “o” in the above example, but
> includes NAs, because the grid-(point) layer is greater than the Polygons.
> Having a look at the SpatialPointsdataframe shows that the column with the
> interesting information is called: “PNSA1145.asc”. Thus I try:
>    R1000m$new<- aggregate(raster_data$PNSA1145.asc, list(overlay_1), mean)$
> PNSA1145.asc
> This doesn’t show me any error, but nothing changed within R1000m.
> possible Problems:
> # rastergrid have lower resolution than Polygons ->  should I use
> disaggregate?
> # is the overlay correct applied? Does it make sense like:  overlay(R1000m,
> raster_data)? Should I use "extract"?
> # raster_data and R1000m do not overlay on each point: small parts of R1000m
> are not overlayed.
> I am extremly thankful for any ideas and information you could give me.
> Kind regards
> Dieter Mayr
> --
> View this message in context: http://r-sig-geo.2731867.n2.nabble.com/converting-grid-objects-to-spatial-polygon-objects-and-export-as-shapefile-tp4143331p6807877.html
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