71 lines
2.1 KiB
Python
71 lines
2.1 KiB
Python
#!/usr/bin/env python
|
|
|
|
from agate.aggregations import Aggregation
|
|
from agate.aggregations.has_nulls import HasNulls
|
|
from agate.aggregations.variance import Variance, PopulationVariance
|
|
from agate.data_types import Number
|
|
from agate.exceptions import DataTypeError
|
|
from agate.warns import warn_null_calculation
|
|
|
|
|
|
class StDev(Aggregation):
|
|
"""
|
|
Calculate the sample standard of deviation of a column.
|
|
|
|
For the population standard of deviation see :class:`.PopulationStDev`.
|
|
|
|
:param column_name:
|
|
The name of a column containing :class:`.Number` data.
|
|
"""
|
|
def __init__(self, column_name):
|
|
self._column_name = column_name
|
|
self._variance = Variance(column_name)
|
|
|
|
def get_aggregate_data_type(self, table):
|
|
return Number()
|
|
|
|
def validate(self, table):
|
|
column = table.columns[self._column_name]
|
|
|
|
if not isinstance(column.data_type, Number):
|
|
raise DataTypeError('StDev can only be applied to columns containing Number data.')
|
|
|
|
has_nulls = HasNulls(self._column_name).run(table)
|
|
|
|
if has_nulls:
|
|
warn_null_calculation(self, column)
|
|
|
|
def run(self, table):
|
|
return self._variance.run(table).sqrt()
|
|
|
|
|
|
class PopulationStDev(StDev):
|
|
"""
|
|
Calculate the population standard of deviation of a column.
|
|
|
|
For the sample standard of deviation see :class:`.StDev`.
|
|
|
|
:param column_name:
|
|
The name of a column containing :class:`.Number` data.
|
|
"""
|
|
def __init__(self, column_name):
|
|
self._column_name = column_name
|
|
self._population_variance = PopulationVariance(column_name)
|
|
|
|
def get_aggregate_data_type(self, table):
|
|
return Number()
|
|
|
|
def validate(self, table):
|
|
column = table.columns[self._column_name]
|
|
|
|
if not isinstance(column.data_type, Number):
|
|
raise DataTypeError('PopulationStDev can only be applied to columns containing Number data.')
|
|
|
|
has_nulls = HasNulls(self._column_name).run(table)
|
|
|
|
if has_nulls:
|
|
warn_null_calculation(self, column)
|
|
|
|
def run(self, table):
|
|
return self._population_variance.run(table).sqrt()
|