Problem with extract by mask

Discussion created by au on Jun 14, 2010

I'm having trouble with the spatial analyst tool 'extract by mask'. I converted a point dataset into a raster (points at 0.5 degree intervals) and used that raster dataset to extract by mask. I extracted raster cells based on river basin shapefiles (irregular polygons) as masks. This works fine as such but some of the basin shapefiles are too small or or a wrong shape and consequently no raster cells are extracted for these. I have attached a figure of the different layers for clarification.
I need each river basin to have at least one corresponding raster cell so could you please suggest a way to get round this problem? Is is possible to adjust the area that the shapefile needs to cover in each raster cell in order to be extracted  (e.g. assuming that at the moment it is only picked up if it covers at least 50% of the raster cell)? Or is there possible another tool I could use?
Thank you for the help.