具有自定义年初数据集统计信息

你可以使用 xarray.DataArray 它指定了组。一种方法是创建定义组ID的值(年)数组:

# setup sample data
dr = pd.date_range('2015-01-01', '2017-08-23')
foo = xr.Dataset({'data': (['time'], np.ones(len(dr)))}, coords={'time': dr})

# create an array of years (modify day/month for your use case)
my_years = xr.DataArray([t.year if ((t.month < 9) or ((t.month==9) and (t.day < 15))) else (t.year + 1) for t in foo.indexes['time']],
                        dims='time', name='my_years', coords={'time': dr})

# use that array of years (integers) to do the groupby
foo_cumsum = foo.groupby(my_years).apply(lambda x: x.cumsum(dim='time', skipna=True))

# Voila!
foo_cumsum['data'].plot()