Hi Maurizio , library(gstat) idw.out <- idw(z~1, elev, grd, idp = 2) this is my code snippet, I have "elev" is SpatialPointsDataFrame object and "grd" is SpatialPixels object. Netra -- View this message in context: http://r-sig-geo.2731867.n2.nabble.com/idw-tp7584975p7584977.html Sent from the R-sig-geo mailing list archive at Nabble.com.