Thanks Giovanni the layer parameter wasn't added automatically by grass and it was selected by default. I opened a tiket in qgis bug tracker for the grass plugin problem
http://hub.qgis.org/issues/4750 pietro -- View this message in context: http://osgeo-org.1803224.n2.nabble.com/Help-in-using-Grass-plugin-to-interpolate-point-data-tp7150158p7154730.html Sent from the qgis-user mailing list archive at Nabble.com. _______________________________________________ Qgis-user mailing list Qgis-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/qgis-user