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<br>Many thanks for the fast replies,<br>
<br>
@ Roger : polygons and raster are ok (see attached file).<br><br>@ Johannes : I have already try this but the result was not satisfying, using a SpatialPointsDataFrame do not solve the problem as the points are not inside the polygon (see attached file).<br><br>I guess the problem arises because of the raster resolution that is to large ....<br><br>Any suggestion would be appreciated,<br><br>Please find attached a plot showing the raster (image), the polygon and the centroid of the raster cells : <br><br>image(grid, axes=TRUE)<br>plot(pol, add=TRUE)<br>points(coordinates(grid))<br><br>Regards,<br><br>Laure.<br> <br /><hr />Avec Internet Explorer, surfez en toute discrétion sur internet <a href='http://clk.atdmt.com/FRM/go/182932252/direct/01/' target='_new'>Cliquez ici !</a></body>
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