class Mean(Aggregation):
"""
Calculate the mean of a column.
:param column_name:
The name of a column containing :class:`.Number` data.
"""
def __init__(self, column_name):
self._column_name = column_name
self._sum = Sum(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(
'Mean 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):
column = table.columns[self._column_name]
sum_total = self._sum.run(table)
return sum_total / len(column.values_without_nulls())
class Mean(Aggregation):
"""
Calculate the mean of a column.
:param column_name:
The name of a column containing :class:`.Number` data.
"""
def __init__(self, column_name):
self._column_name = column_name
self._sum = Sum(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('Mean 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):
column = table.columns[self._column_name]
sum_total = self._sum.run(table)
return sum_total / len(column.values_without_nulls())
def run(self, table):
"""
:returns:
:class:`decimal.Decimal`
"""
# If the user has provided a total, use that
if self._total is not None:
total = self._total
# Otherwise compute the sum of all the values in that column to
# act as our denominator
else:
total = table.aggregate(Sum(self._column_name))
# Raise error if sum is less than or equal to zero
if total <= 0:
raise DataTypeError(
'The sum of column values must be a positive number')
# Create a list new rows
new_column = []
# Loop through the existing rows
for row in table.rows:
# Pull the value
value = row[self._column_name]
if value is None:
new_column.append(None)
continue
# Try to divide it out of the total
percent = value / total
# And multiply it by 100
percent = percent * 100
# Append the value to the new list
new_column.append(percent)
# Pass out the list
return new_column
def __init__(self, column_name):
self._column_name = column_name
self._sum = Sum(column_name)
def __init__(self, column_name):
self._column_name = column_name
self._sum = Sum(column_name)
