[R-sig-Geo] ESRI ASCII Grid file shifted
KAM Tin Seong
tskam at smu.edu.sg
Tue Jun 19 05:21:23 CEST 2007
> Hi all,
>
> I am new to R and would like to get some advice. I performed kernel
> density estimation using spatstat. The point data (i.e. drawing) is
> in ESRI shapefile format. It was read in using "readShapePoints" of
> maptools. After the analysis, the result was exported using
> "writeAsciiGrid" of maptools. The entire codes are as follows:
>
> library(spatstat)
> library(maptools)
> d=readShapePoints("C:/TEMP/shp/drawing")
> w = owin(c(-15000,16500),c(-15000,15000))
> dppp=as(d["DHL_Sales"], "ppp")
> cpt = ppp(x=dppp$x, y=dppp$y, marks=dppp$marks, window=w)
> plot(dppp)
> z = density.ppp(cpt, 500)
> image(z)
> gridded_z = as.SpatialGridDataFrame.im(z)
> writeAsciiGrid(gridded_z, "C:/TEMP/grid/KDE_Store1.asc")
>
> When I compared the exported grid file (i.e. KDE_Store1) with the
> input shapefile (i.e. drawing), I notice that there is a shift in the
> grid file. Refer to the enclosed screenshoot. I wonder if anyone can
> advice me whats went wrong.
>
> Thanks in advance.
>
> <<KDE1.jpg>>
> Dr Kam Tin Seong
> Practice Associate Professor
> School of Information Systems
>
> Singapore Management University
> 80 Stamford Road
> Singapore 178902
> e-mail: tskam at smu.edu.sg
> DID: + 65 6828 0932
>
>
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