[R-sig-Geo] Defining a grid for interpolations ?
edzer.pebesma at uni-muenster.de
Tue May 27 15:34:45 CEST 2008
Mauricio Zambrano wrote:
> Dear Paul and Edzer,
> Thanks a lot for your answers.
> Before reading the solution proposed by Paul, I had tried with:
> # reading the boundary of the catchment
> catchment <- readShapePoly("only_catchment.shp")
> catchment.grid <- spsample(catchment, cellsize=100, offset = c(0.5,
> 0.5)) # reading the boundary of the catchment
> and then I did an IDW interpolation with:
> pp.idw <- krige(PP_DAILY_MEAN_MM~1, meteo, catchment.grid)
> and it works.
> However, after reading your solution, I realised that I didn't use the command:
> but I got an interpolation anyway.
> Where is performed the interpolation when I don't use a gridded grid (
> gridded(catchment.grid) ) ?
it is actually
gridded(catchment.grid) <- TRUE
that changes the object, if it not gridded.
For interpolation, it doesn't matter whether you loop over a set of
points, or a set of points on a grid.
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