[R-sig-Geo] ESRI ASCII Grid file shifted

[KAM Tin Seong]

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>>  <<drawing.zip>> 

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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