Description
This example shows: How to use an iterator on lat/lon/values and query the bitmap for missing values (rather than compare each value with the missingValue key)
Source code
grib_iterator_bitmap.py
# # (C) Copyright 2005- ECMWF. # # This software is licensed under the terms of the Apache Licence Version 2.0 # which can be obtained at http://www.apache.org/licenses/LICENSE-2.0. # # In applying this licence, ECMWF does not waive the privileges and immunities granted to it by # virtue of its status as an intergovernmental organisation nor does it submit to any jurisdiction. # # Description: How to use an iterator on lat/lon/values and query the bitmap # for missing values # (rather than compare each value with the missingValue key) # import traceback import sys from eccodes import * VERBOSE = 1 # verbose error reporting def example(INPUT): f = open(INPUT, 'rb') while 1: gid = codes_grib_new_from_file(f) if gid is None: break iterid = codes_grib_iterator_new(gid, 0) bitmapPresent = codes_get(gid, 'bitmapPresent') if bitmapPresent: # Get the bitmap array which contains 0s and 1s bitmap = codes_get_array(gid, 'bitmap', int) # Do some sanity checking assert len(bitmap) == codes_get_size(gid, 'values') assert len(bitmap) == codes_get(gid, 'numberOfDataPoints') i = 0 while 1: result = codes_grib_iterator_next(iterid) if not result: break [lat, lon, value] = result sys.stdout.write("- %d - lat=%.6e lon=%.6e value=" % (i, lat, lon)) # Consult bitmap to see if the i'th value is missing if bitmapPresent and bitmap[i] == 0: print("missing") else: print("%.6f" % value) i += 1 codes_grib_iterator_delete(iterid) codes_release(gid) f.close() def main(): try: example(sys.argv[1]) except CodesInternalError as err: if VERBOSE: traceback.print_exc(file=sys.stderr) else: sys.stderr.write(err.msg + '\n') return 1 if __name__ == "__main__": sys.exit(main())
grib_iterator_bitmap.c
/* * (C) Copyright 2005- ECMWF. * * This software is licensed under the terms of the Apache Licence Version 2.0 * which can be obtained at http://www.apache.org/licenses/LICENSE-2.0. * * In applying this licence, ECMWF does not waive the privileges and immunities granted to it by * virtue of its status as an intergovernmental organisation nor does it submit to any jurisdiction. */ /* * Description: How to use an iterator on lat/lon/values and query the bitmap * for missing values * (rather than compare each value with the missingValue key) */ #include <stdio.h> #include <stdlib.h> #include <string.h> #include <assert.h> #include "eccodes.h" static void usage(const char* prog) { printf("Usage: %s grib_file\n",prog); exit(1); } int main(int argc, char** argv) { FILE* in = NULL; int err = 0; double lat,lon,value; int n=0; size_t bmp_len = 0, values_len = 0; char* filename = NULL; long bitmapPresent = 0; long *bitmap = NULL; double *values = NULL; codes_handle *h = NULL; codes_iterator* iter=NULL; if (argc != 2) usage(argv[0]); filename=argv[1]; in = fopen(filename,"r"); if(!in) { fprintf(stderr, "ERROR: unable to open file %s\n",filename); return 1; } while ((h = codes_handle_new_from_file(0, in, PRODUCT_GRIB, &err)) != NULL ) { if (err != CODES_SUCCESS) CODES_CHECK(err,0); CODES_CHECK(codes_get_long(h,"bitmapPresent",&bitmapPresent),0); if (bitmapPresent) { CODES_CHECK(codes_get_size(h,"bitmap",&bmp_len),0); bitmap = (long*)malloc(bmp_len*sizeof(long)); CODES_CHECK(codes_get_long_array(h,"bitmap",bitmap,&bmp_len),0); printf("Bitmap is present. Num = %lu\n", bmp_len); } /* Sanity check. Number of values must match number in bitmap */ CODES_CHECK(codes_get_size(h,"values",&values_len),0); values = (double*)malloc(values_len*sizeof(double)); CODES_CHECK(codes_get_double_array(h,"values",values,&values_len),0); if (bitmapPresent) { assert(values_len==bmp_len); } /* A new iterator on lat/lon/values is created from the message handle h */ iter=codes_grib_iterator_new(h,0,&err); if (err != CODES_SUCCESS) CODES_CHECK(err,0); n = 0; /* Loop on all the lat/lon/values. Only print non-missing values */ while(codes_grib_iterator_next(iter,&lat,&lon,&value)) { /* Consult bitmap to see if the n'th value is missing */ int is_missing_val = (bitmapPresent && bitmap[n] == 0); if (!is_missing_val) { printf("- %d - lat=%f lon=%f value=%f\n",n,lat,lon,value); } n++; } /* Check number of elements in iterator matches value count */ assert(n == values_len); codes_grib_iterator_delete(iter); codes_handle_delete(h); } fclose(in); return 0; }