At the Esri International User Conference this year, an attendee came to the analysis island to ask “how do I create a rank field?”. They had run the Generate Near Table geoprocessing tool (see illustration of table below) and were looking for a way to further rank the distances. Ideally, the table would be updated to include a RANK field starting at ‘1’ for the smallest distance for each PATIENT and increasing sequentially based on the distance. The rank could then be used to facilitate further review and reporting. We were able to come up with the addRanks function below in a few minutes automating a key missing piece of the user’s workflow.
import arcpy def addRanks(table, sort_fields, category_field, rank_field='RANK'): """Use sort_fields and category_field to apply a ranking to the table. Parameters: table: string sort_fields: list | tuple of strings The field(s) on which the table will be sorted. category_field: string All records with a common value in the category_field will be ranked independently. rank_field: string The new rank field name to be added. """ # add rank field if it does not already exist if not arcpy.ListFields(table, rank_field): arcpy.AddField_management(table, rank_field, "SHORT") sort_sql = ', '.join(['ORDER BY ' + category_field] + sort_fields) query_fields = [category_field, rank_field] + sort_fields with arcpy.da.UpdateCursor(table, query_fields, sql_clause=(None, sort_sql)) as cur: category_field_val = None i = 0 for row in cur: if category_field_val == row: i += 1 else: category_field_val = row i = 1 row = i cur.updateRow(row) if __name__ == '__main__': addRanks(r'C:\Data\f.gdb\gen_near_table_patients2hosp', ['distance'], 'patient', 'rank')
Note: dBase (and shapefiles) does not support ORDER BY as used above by arcpy.da.UpdateCursor’s sql_clause argument.