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