def __init__(self, source, rowvaluesatt, colvaluesatt, values,
aggregator=None, nonevalue=0, sortrows=False):
"""Arguments:
- source: the data source to pull data from
- rowvaluesatt: the name of the attribute that holds the values that
appear as rows in the result
- colvaluesatt: the name of the attribute that holds the values that
appear as columns in the result
- values: the name of the attribute that holds the values to aggregate
- aggregator: the aggregator to use (see pygrametl.aggregators). If not
given, pygrametl.aggregators.Sum is used to sum the values
- nonevalue: the value to return when there is no data to aggregate.
Default: 0
- sortrows: A boolean deciding if the rows should be sorted.
Default: False
"""
self.__source = source
self.__rowvaluesatt = rowvaluesatt
self.__colvaluesatt = colvaluesatt
self.__values = values
if aggregator is None:
from pygrametl.aggregators import Sum
self.__aggregator = Sum()
else:
self.__aggregator = aggregator
self.__nonevalue = nonevalue
self.__sortrows = sortrows
self.__allcolumns = set()
self.__allrows = set()
