Hi,
When I call:
over(spPolyDf, spGridDf)
The function seems to be returning the spGridDf$band1 value for the first
grid cell that is contained in each polygon.
What I would like is an overlap-area weighted average (or some provided
function like sum) of all the grid cells contained (or partial
Kenny,
Here is an alternative route
library(raster)
states <- shapefile("cb_2013_us_state_20m.shp")
tMaxGrid <- raster(unzippedFiles[1])
x <- extract(tMaxGrid, states)
This returns a list of the length of states. Each list element has a
vector with the grid cell values.
For a mean do
xs <- ext
On 04/14/2015 01:27 AM, Kenny Bell wrote:
> Hi,
>
> When I call:
>
> over(spPolyDf, spGridDf)
>
> The function seems to be returning the spGridDf$band1 value for the first
> grid cell that is contained in each polygon.
This is documented; you can use returnList = TRUE to get the list of
value
Thanks so much for all this. Yes, I'm after the area weighted averages. The
eventual application is to aggregate a 2.5 arcminute temperature grid up to
a zip-5 polygon, many of which overlap only 2-3 grid cells.
On Mon, Apr 13, 2015 at 10:47 PM, Edzer Pebesma <
edzer.pebe...@uni-muenster.de> wrote
On 04/14/2015 06:58 PM, Kenny Bell wrote:
> Thanks so much for all this. Yes, I'm after the area weighted averages. The
> eventual application is to aggregate a 2.5 arcminute temperature grid up to
> a zip-5 polygon, many of which overlap only 2-3 grid cells.
One approach would be to use spsample
Thanks so much for this.
The code does work. However, the gIntersection() stage is very time
intensive, so I will continue to use my own code that relies on joinPolys
in PBSmapping (faster).
It also allows you to store the rows/weights of the grid so that
aggregating many grids to polygons is fea
