cpc_get_rawdata         Download rainfall data from CPC for the time
                        period of interest
cpc_read_rawdata        Read downloaded raw rainfall data from CPC
raincpc                 Obtain and analyze rainfall data from the
                        Climate Prediction Center.
sdm_as_asc              Raster conversion functions
sdm_asc_from_raster     Raster conversion functions
sdm_extract_data        Spatial Join of Points with Raster Grids
sdm_getXYcoords         Computes the X and Y Coordinates of the Pixels
                        of a Raster Map
sdm_raster_from_asc     Raster conversion functions
